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Recording properties of a concentric needle electrode for electromyography as measured in an electrolytic… Sutter, Martin 1981

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RECORDING  PROPERTIES OF A CONCENTRIC  NEEDLE ELECTRODE FOR AS MEASURED  ELECTROMYOGRAPHY  I N AN E L E C T R O L Y T I C TANK MODEL  by  MARTIN SUTTER D i p ] . . E l . - I n g . ETH, S w i s s F e d e r a l Zftrich,  A  Institute  Switzerland,  of Technology  1977  T H E S I S SUBMITTED IN P A R T I A L F U L F I L M E N T OF THE  THE.REQUIREMENTS  FOR  DEGREE OF MASTER OF A P P L I E D  SCIENCE  in  THE  F A C U L T Y OF GRADUATE S T U D I E S  (Department  We  THE  of E l e c t r i c a l  Engineering)  accept t h i s t h e s i s as conforming to the required standard  U N I V E R S I T Y OF B R I T I S H July ©  Martin  COLUMBIA  1981  S u t t e r , 1931  In  presenting  requirements  this thesis f o r an  of  British  it  freely available  agree for  that  understood for  Library  shall  for reference  and  study.  I  for extensive  that  h i s or copying  f i n a n c i a l gain  be  her or  shall  publication  not  be  DE-6  (2/79)  of  Columbia  make  further this  thesis  head o f  this  It  my  is  thesis  a l l o w e d w i t h o u t my  of  The U n i v e r s i t y o f B r i t i s h 2075 Wesbrook P l a c e V a n c o u v e r , Canada V6T 1W5  the  representatives.  permission.  Department  copying of  g r a n t e d by  the  University  the  p u r p o s e s may by  the  I agree that  permission  department or  f u l f i l m e n t of  advanced degree at  Columbia,  scholarly  in partial  written  ii  ABSTRACT  The do  not  the  widely  used  exactly  correspond  electrode  muscle,  and  voltage.  induces  the  In  order  dipole  muscle ped  fiber  with  a  model  concentric  and  the  the  needle  a  were  an  introduced  fiber  and  evinced  conventional  of  in  original  a  perfect  muscle. field  The  unit  of  the  tank  reference  equivalent.  so  that  were the  the  Three  core,  the  concentric  or  needle  potentials.  improvements  in  to  field  for  cannula  and  as  a  a motor u n i t .  with  electrode  the was  i t s recording  out.  model a  and  The  were  not  single  was  map-  d i s t r i b u t i o n as  available  electrode  zero  have  a  a  complete  measurements.  insulator surrounding  Finally,  needle  which  carried  sub-assemblies  depth  of the  of  potential field  "true"  quantified.  single fiber  presence  electrode  employed The  separately  insertion  concentric  was  that  distribution in  distorting properties,  established.  unit  design.  the  as  experimentally  substantial  signal  electromyograms  e x p e r i m e n t a l - i n v e s t i g a t i o n was  electrode  new  produces  the  signal  electrode  the  motor  electrode  electrolytic  a nearby  by  of act  the  motor  function  investigation, a  which  a  was  arrangement of  tortions  the  as  true  not  distorting properties  determined  single  as  comparisons  cannula,  spatial  the  i n an  point-shaped  for  field  assess  established,  well  basis  The  to  does  generator as  to  needle  distortions  cannula  been n u m e r i c a l l y A  concentric  the  core  potential  function The  of  the  overall  dis-  measured  knowledge designed fidelity  was  for  both  gained  and  in  tested  compared  to  iii  T A B L E OF  CONTENTS Page  ABSTRACT  .  i i  L I S T OF FIGURES  . . .  v i  L I S T OF SYMBOLS  viii  ACKNOWLEDGEMENT  ix  I.  II.  INTRODUCTION  1  1.1  The M u s c l e  1.2  The S i n g l e  1.3  Limitations of the Single  1.4  EMG  1.5  The C o n c e n t r i c  1*6  T h e P r o b l e m o f CNEMG M e a s u r e m e n t  • • F i b e r Model  Electrodes  2 4  Fiber Laboratory  Model  . . . . . .  8  . . . . .  10  Needle Electrode  13 15  EXPERIMENTAL APPARATUS  18  2.1  The M u s c l e F i b e r  Analog  19  2.2  The E l e c t r o l y t i c  Tank  20  2*3  Verification  2.4  Geometrical  o f t h e Tank  Properties  25  and F h y s i c a l S i m i l a r i t y  The M e t a l - T i s s u e  . . . . . . .  Interface  .  S h u n t i n g o f Volume C o n d u c t o r C u r r e n t s Wall  . . . . . . . . . .  Potential  29  Averaging  . . . .  Measurements  . . . . . . . . . . . . . . . .  Electrodes Point  Electrode  The  Point  Electrode  34 36  S u r r o u n d e d by an " I n s u l a t i n g W a l l " .  o f t h e CN E l e c t r o d e  Model  .  37  . . . . .  38  'Core'  39  'Core & I n s u l a t i o n "  . .  Complete  . . . . . . . . . . . . .  The  30 30  . .  The  Development  27 28  Effect  Verification 2.5  25  Electrode  . . . . . . . . . . . .  Reference Electrode  Treatment of the Leading-off  Surface  40 41 .  42  •  43  iv  Page 2.6  Electrical Dipole The  Apparatus  44  Source Generator . . . .  Current  Source  The M e a s u r i n g S e t - u p The  44  . . . . . .  45  . . . .  46  . . . . . . .  Amplifier  49  Miscellaneous  III.  . . . . . . .  .  . . . . . . .  50  RESULTS & DISCUSSION 3.1  General  52  Remarks  Recording Axial  53  Distance  Distance  z  r  . . . . .  . . .  . . . .  V e r t i c a l Distance y I n s e r t i o n Depth d Relative Position of Electrode PTPA PTPD  and  Fibers . . . . . . . . . . . . . . . . . . .  Symbols  The W a l l  Effect  3.3  The  'Core* A l o n e  3.4  The  'Core & I n s u l a t i o n '  Assembly  3.5  The  Complete  Needle E l e c t r o d e  3.6  Single  Fiber  .  .  Potential  3.8  The  3.9  Motor  Motor  Unit  . . . .  . .  Cannula  Potential  Peak-to-peak  . . . . . . . .  63 65  Cannula Insertion  Measurements  Duration  Electrode  • •  Peak-to-peak Amplitude Duration  Duration  70  . . . . . . .  81  . . . . . . . . . . . . .  81  . . . .  . . . .  . . . . .  . . . .  • . . .  . • • .  83 83  • • •  85  . . . . . . . . . .  89  . . . . . . . . . . . . . . . . .  91  Design  Potential  Peak-to-peak  Depths  78  Duration  Cannula  63  . . . . . . . . . . . . . . . . . .  Model  Potential  Spike  . . .  61  70  Unit  Special  . . .  Duration  Peak-to-peak Amplitude  3.10  . . .  57 58  .  Amplitude  of Different  Spike  . . . . . . . .  Measurements  Peak-to-peak D u r a t i o n Spike  57 . •  Concentric  Peak-to-peak  56 56  3.2  Effect  54 54 54 55 56 56  .  SD Key  3.7  53  . . . . . . . . . .  87  . . . . . . . . . . . . . . . . . .  97 97  V  Page IV.  CONCLUSIONS AND RECOMMENDATIONS 4.1  Conclusions Field Distortions Overall  4.2  BIBLIOGRAPHY APPENDIX  . 1 0 4  Distortions  105 105 . . . . . . . . . . .  107  Cannula P o t e n t i a l E l e c t r o d e Improvements  108 109  Summary  110  Recommendations  . .  . . . . . .  . . . . . . . . .  110  113 118  vi  L I S T OF  FIGURES  Page 1.1  The  Action  Potential  . . . . . . . . . .  1.2  The  Single  Fiber  1.3  The  Potential  1.4  Extracellular Action  1.5  Action  1.6  The C o n c e n t r i c  1.7  The  D I S A 13K53 CN  2.1  The  Dipole  2.2  The  Electrolytic  2*3  The  Fiber  2.4  Computed  2.5  The M e t a l - T i s s u e  2.6  Shunting, Wall  2.7  The  Electrode  2.8  The  Complete  2.9  The  Point  2.10  The  'Wall E f f e c t E l e c t r o d e '  2.11  The  Core  2.12  Core & I n s u l a t i o n ;  2.13  The  2.14  Equivalent.  2.15  The  3.1  Nomenclature of the R e l a t i v e  3.2  Front  3.3  PTPA v s . r , ' C o r e ' ; F r o n t  3.4  PTPA v s . r , ' C o r e & I n s u l a t i o n " ;  3.5  Relative  PTPA v s . r , ' C o r e ' , ' C o r e & I n s u l a t i o n ' ;  3.6  Relative  PTPA v s . r , C o m p l e t e  CNE;  Front  SFP  3.7  Relative  PTPA v s . r , C o m p l e t e  CNE;  Front  and Back  SFP  3.8  PTPD v s . r ,  'Core & I n s u l a t i o n ' ,  Complete  CNE;  3.9  PTPD v s . r , C o m p l e t e  Dipole  3  Concept  5  Distribution  • •  6  . . . . . .  . . . .  7  . . . . . . .  . .  8  Potentials  P o t e n t i a l Nomenclature Needle Electrode  . . . . . . . . . .  13  Electrode  14  Model  20 Tank N o m e n c l a t u r e  . . . . .  Frame and Measured  Isopotential  Interface  Lines  . . . . .  22  '  24  . . . .  26  . . . . . .  28  E f f e c t and A v e r a g i n g  32  Holder  35  P o s i t i o n i n g Assembly  . . .  36  Electrode  37 .  38 40  Complete  Electrode  . . . . . .  41  Reference Electrode Circuit  Electrical  and Back  43  of E l e c t r o l y t e , Electrode  and A m p l i f i e r  . . . .  47  Apparatus  Fibers;  'Core',  50  Electrode  Insertion  CNE;  SFP  Position  Depth  . . . .  53  . . . . . . . . . . . . .  55  . .  Front  .  Front  SFP  and Back  59 60  SFP  Front  SFP  . . .  62 64  . . .  66 Front  SFP  .  67  . .  69  vii  Page 3.10  SD v s . r , ' C o r e ' ,  3.11  SD v s . r , C o m p l e t e CNE;  3.12  C a n n u l a PTPA v s . r , D i f f e r e n t  Insertion  Depths; Front  SFP  (y =  0).  74  3.13  C a n n u l a PTPA v s . r . D i f f e r e n t  Insertion  Depths; Front  SFP  (y t  0).  75  3.14  Relative  3.15  S p a t i a l Arrangement o f t h e Motor U n i t  3.16  Relative  3.17  PTPA v s . r , C o m p l e t e CNE;  3.18  SD v s . r , C o m p l e t e CNE;  3.19  Type  3.20  T y p e I I New  3.21  Relative  Cannula P o t e n t i a l  3.22  Relative  Cannula P o t e n t i a l v s . z,  3.23  Relative  Cannula P o t e n t i a l v s . r , R e g u l a r and Type I / I I ;  Front  Cannula P o t e n t i a l v s . z; Front  Front  C o m p l e t e CNE;  a n d Back  C a n n u l a PTPA v s . r ; F r o n t  I New  Front  'Core & I n s u l a t i o n ' ,  Front  SFP . .  71 72  SFP  77  SFP Model  Front  . . . . . . . . . . .  S F P a n d MUP  . .  79 82 84  SFP a n d MUP  86  S F P a n d MUP  88  Design  88  Design vs. z,  Regular  and Type  R e g u l a r and Type  SFP  90  . . . .  92  I / I I ; Front I ; MUP  93  SFP a n d MUP  3.24  PTPA v s . r , R e g u l a r a n d T y p e  I / I I ; Front  3.25  PTPA v s . r , R e g u l a r  I / I I ; MUP  3.26  Relative  3.27  SD v s . r , R e g u l a r  and Type  I / I I ; Front  3.28  SD v s . r , R e g u l a r  and Type  I / I I ; MUP  3.29  Relative  A.l  Circuit  of the Current  A.2  Circuit  of the Amplifier  A.3  Signal  and Type  PTPA v s . r . R e g u l a r a n d T y p e  SD v s . r , R e g u l a r  Flow C i r c u i t  and Type  96 98  I / I I ; MUP SFP  . . . . . . . . . . . .  99 101  . .  103  I / I I ; MUP  Source  ( I s o l a t i o n , CMR)  95  SFP  . . . . . . . . . . .  119 120  .  . . . . .  121  viii  L I S T OF SYMBOLS  Symbol AP CNE,  action CN e l e c t r o d e  potential  2  concentric  needle  CNEMG  concentric  needle  core  the  central  wire  electrode  insulation'  'core v s . remote*  'cannula  v s . remote'  o f t h e CNE  the  signal  the  16  i i ,  consisting 39  40  the s i g n a l measured between t h e core and the reference e l e c t r o d e , w i t h t h e c o m p l e t e CNE  trode, v s . cannula'  15  the model e l e c t r o d e c o n s i s t i n g o f t h e core surrounded by t h e insulation  cannula  'core  13  electromyography  the model e l e c t r o d e s o l e l y of the core •core &  F i r s t occurrence o r e x p l a n a t i o n , page  Meaning  61  measured between t h e  and the reference with  t h e complete  differential  between t h e c o r e  signal  elecCNE  61  measured  and t h e cannula  w.r.t. t h e reference e l e c t r o d e , with DISA  t h e complete  manufacturer o f  CNE  61  electromyographic  electrodes  41  EMG  electromyography  2  MU  motor  4  MOP  motor u n i t  PTPA  peak-to-peak amplitude  PTPD  peak-to-peak  SF  single  fiber  SFEMG  single  fiber  SFP  single  fiber  SD  spike  unit potential  duration  7 ,  8,  56  8,  56 4  electromyography  12  potential  duration  7 8,  56  ix  ACKNOWLEDGEMENTS  I his  should  constant  documentation Many the Kathy  like  t o express  encouragement would  thanks  construction Brindamour  never  to Chris of  the  and G a i l  my  and have  gratitude  t o Dr. Peter  invaluable been  Sheffield  the project  Without and  this  possible.  a n d Dave  experimental Hrehorka  suggestions  D. L a w r e n c e .  Fletcher  apparatus.  f o rtheir  fast  who I  am  assisted also  me  during  grateful  and e f f i c i e n t t y p i n g  to  of the  thesis. My s t a y  i n Canada  was made p o s s i b l e  b y a UBC G r a d u a t e  Student  Fellowship.  1  I  do n o t knew what  to  myself  on  the seashore,  then  I seem  finding  shell  than  truth  lay  a  I may  t o have  appear been  and d i v e r t i n g smoother  a boy  myself  pebble  ordinary, whilst a l l  t o the world, but only  the  undiscovered  or  playing  i n now a  great  and  prettier ocean  before  of me.  I s a a c Newtdn (Memoirs o f Newton, B r e w s t e r )  I.  INTRODUCTION  2  1.1  The M u s c l e For  of  well  over  L u i g i Galvani,  some  sort  ment  and  valuable ment  hundred  of e l e c t r i c a l recording tool  years,  i t h a s b e e n known  of  this  signal  beginning  that  activity.  Today  electromyography activity",  involved  is a  have  l e g experiments  i s accompanied  (EMG), well  disorders.  and experiments  processes  the frog  contraction  of neuromuscular  analysis  of the electrochemical  with  a muscle  "electrical  f o r the diagnosis  techniques,  ledge  two  by  t h e measure-  established  Improved  measure-  l e d t o a profound  i n the i n i t i a t i o n  and  of  know-  muscular  contractions. Membranes ally  more  fusion, CI",  the  negative  osmotic  K ,  membrane  potential  of  An  action  and  others)  and muscle  This  forces  potential  (AP)  by l o c a l  resistivity  ionic  a l s o ' due  between  potential  t h e ends  short  temporary  local  changes certain  of  (EPP).  change  after  trigger a velocity  "chain 1  f o r a short  motor  fiber.  which  the  reaction"  departing  The p r o p a g a t i o n v e l o c i t y o f AP's a b o u t 4 m/s, s e e s e c t i o n 1.2.  As  in  to  an  t o 90  period  flows, ions,  end  cell  temporary  In a muscle  The  the muscle  mV  is a  to the various  are  electric-  and body active  of  fluid  ion  fiber  so t h a t either  change  change  i s usually shows,  potential a n AP  biceps  (Na , +  across  the resting the  resting  see F i g .  is initiated  by  by a  located  t h e AP  small  brachii  the  the  midway  i s only  i s restored.  from  1.1.  changes  i s called  travels along  direction  i n t h e human  of  o f time,  this  F i g . 1.1  resting  called  i s made p o s s i b l e  which  plate  mV,  dif-  transport  The p o t e n t i a l d i f f e r e n c e  o f 60  current  cells,  i s due t o a n e q u i l i b r i u m  of the ionic  and  i n the order  i n the resting p o t e n t i a l .  plate  a  outside.  whose p o l a r i t y i s r e v e r s e d  AP, c h a r a c t e r i z e d  change  at  ions  i s normally  t h e membrane  end  than  i . e . nerve  - t h e s o - c a l l e d s o d i u m - p o t a s s i u m pump.  potential.  The  inside  cells,  and e l e c t r o s t a t i c  protein  +  system  of excitable  a  The  the fiber motor  i s on  end  average  3  K barrier down, K* leaves cell + 5 0  Na* barrier restored  > 1  Na* barrier J down, Na* \ enters cell  j  J3  E  /  hreshold (citation  **-  5  V  - 7 0  /  Excess K* out of cell-diffusion of ions and sodium-potassium pump restores ionic balance  J  t  1  i  Shock applied  Time (msec)  The transmembrane voltage and the f l u x e s d u r i n g the a c t i o n p o t e n t i a l . From C a r l s o n ( 1 9 7 7 ) , p . 4 1 .  plate.  T h e AP i s a b s o r b e d  reflected. triggers single  a  An  AP  series  AP w i l l  a t t h e end o f t h e muscle  releases of  events  produce  Ca  + +  that  into  the cytoplasm  result  a s i n g l e muscle  in a fiber  Ionic  fiber of  muscle twitch.  and i s t h e r e f o r e not the muscle  fiber  fiber  contraction.  The r a t e  and A  of f i r i n g of  4  AP's  as w e l l  smoothness single all  of  muscle  fibers  MU's. a  fibers  and  i n terms  training in  routine  EMG.  muscle and  2  t o one  There  The  characteristic  can  measured ferent  sampled  the  Theoretically, potential logic  fiber.  generator  (1947)  and  was  by  single  muscle current  fiber  (when  model  the  that  I,  which  can  them.  accurate  body  of  Therefore,  contains  other  a c t i v a t e one frequently  of  many  functioning of  i n t e r p l a y with  is  during create  inserted electrode  the  cell  could  muscles.  s i n g l e MU,  sampled  literature  in  that  for  human  discusses  by  does  be  along  within  not  the  The  the  depicted  field  potential  cell)  is  dif-  in Fig.  1.1.  the e x t r a c e l l u l a r l y  picked  used today t o describe  the  d e v e l o p e d by  (1957) as  muscle  can  into the tissue  muscle. enter  as  basically  modeled  a MU  the  membrane  Rosenfalck  spread  a time v a r y i n g p o t e n t i a l  simulate  was  a n AP,  into  i s frequently  simply  travels  The a v e r a g e number o f f i b e r s f i b e r s , s e e s e c t i o n 1.2.  flow  tissue,  reformulated (SF)  that  electrodes  and the muscle later  an  number  in detail.  There they  innumerable models The  which  considerable  p o t e n t i a l across  shape.  the  is a  Each muscle  allows  and  (MU)  innervates  to voluntarily  muscle  currents  extracellularly  from  that  unit  and  Model  the muscle be  motor  i n concert.  movement  brachii a  A  activity  anatomy and p h y s i o l o g y  Single Fiber  which  contract  possible  exists  The  surrounding  MU  strength,  biceps  involved determine the strength  cc-motorneuron  efferent neural  of  fibers  contraction.  the  i t i s easily  the  neuromuscular  stant  whole  belonging  example  1.2  a  Afferent  muscle  With  a s t h e number o f m u s c l e  vary  a  and  Plonsey  dipole fiber  Lorente  f r o m a few  the  biode  N6  (1969).  A  generator  at  up  of  con-  propagation  t o many  hundred  velocity tropic  of  an  AP.  volume  and  isotropy  is  non-linear  (z,  do  not  and  the  of  quite  0.9%  specific  centre  conductivity  and  the  a.  specific The  by  a  In  homogenous reality,  conductivity  volume  conductor  in a  cylindrical  (or  and  iso-  homogeneity resistivity)  i s represented  by  solution.  1.2)  of  i s represented  dependent.  saline (Fig.  tissue  apply,  frequency  potential  r) with  muscle  conductor  a physiological The  The  at  the  a  point  dipole  P  i n i t s o r i g i n i s given  coordinate  system  by  (1.1)  where  a  stant  current.  i s the  conductivity The  source  of  the  and  saline,  sink  (±1)  2s  of  the  the  dipole  dipole  length  i n the  and  I the  laboratory  conmodel  r  z  r  s  5 0  FIqure  consist  of  diameter  of  of  the  two  small  a muscle  spheres  does  1.2.  metal  The  -I  single  spheres  fiber.  The  not  affect  z  O  fiber  of  physical the  dipole  concept.  diameter  2a,  corresponding  l i m i t a t i o n imposed  problem,  for  the  by  field  the  to  finite  will  only  the size be  6  c o n s i d e r e d where r > a .  The  whereas s i n f l u e n c e s the  shape o f  values  from  (dipole mm)  the  length  and  a  (1964),  human  2s  =  Figure infinite  0.5  mm)/  1.3  velocity  depicts  a  around the  a determine  I and  the p o t e n t i a l muscle  field.  the  absolute  an  average  0.025 mm  (diameter  of  a muscle  of  4  about  Boyd e t a l . of  the  m/s;  see  of  Buchthal  s  obtained  =  fiber  0.25  2a  (1955),  mm  —  0.05  Ekstedt  (1978).  isopotential  manner  dipole, according to  potential  Experimentally  give  group  illustrate  of  brachii  a —  (1969) and  number) t o  tributed  biceps  propagation  Rosenfalck  values  lines  i n which Eqn.  1.1  the and  (of  which  potential Fig.  there field  is is  an  dis-  1.2.  -> z  FIqure  In at  two  F i g . 1.4 different  generator. less  1.3.  two  extracellular  distances  I t should  pronounced  The d i p o l e and t h e p o t e n t i a l (Isopotential lines). F r o m G e d d e s ( 1 9 7 2 ) , p . 27 1.  be  "peak"  x  1  noted than  and  AP's r  2  shown  parallel  t h a t the for  are  r,.  AP  as  to  for r  distribution  a  the  2  has  f u n c t i o n of  axis a  of  the  smaller  z,  recorded  fixed  dipole  amplitude  and  F1gure  1.4.  An e x t r a c e l l u l a r a c t i o n potential encountered by e x p l o r i n g e l e c t r o d e moving a l o n g l i n e s r, , r p a r a l l e l to the dipole axis (F1g. 1.3). From G e d d e s ( 1 9 7 2 ) , p. 271. 2  The muscle The  e x t r a c e l l u l a r l y recorded fiber  single  generator  fibers  simultaneously form  the  higher MUP  so  fibers  as  well  as  be  noted  as  the  that the  a  the  field  function  of  the  dipole  to  reality;  propagation  of  the  than  of  single  fire  but  of of  the z;  1.5).  velocity.  AP  shape  fixed  sampling  Fig. along The  features is  dipole 1.4)  or  i t s axis  conversion  fiber  their  (MUP). SFP  originate  fields Its  both  are  when a (AP  as  shown  factor  line fixed a  AP's  nearly  is and  the  to  generally shape of  a  constituting  r e l a t i v e to  the  MU.  3.8.  is  a  of  (SFP).  superimposed  amplitude  electrode  single  potentials  amplitude  i d e n t i c a l when  along  from a  individual  s p a t i a l arrangement  the  d i s t i n c t AP  far  potential  a  number a n d  position  as  always  potential  "spiky"  recorded  m o v i n g by  Fig.  MU  so  a b o u t MUP's i s g i v e n i n s e c t i o n  nomenclature  samples (AP  on  a  to  accompanying unit  less  described  referred  to  the  motor  much on  More i n f o r m a t i o n The  that  i t s shape  depend v e r y  are  belonging  so-called  and  and  AP's  Fig.  the  electrode  the  of  1.5.  It  exploring  p a r a l l e l to  function of  in  the  t i m e and  electrode  dipole  samples time,  should  the  axis field  corresponding  z-axis  i s the  AP  ,  8  voltage  A  1 *>  Peak  Baseline Intersection  J ...  \  time  N  1 a.  ,  1 Trough  : i  v/  Pot. Pnase ' Nez. Phase i 1 I I i 1 Rising phue i j Rise-time j  !  n  J •  FIgure  1.3  1.5.  Action potential nomenclature: "spike" denotes the f a s t p o s i t i v e - n e g a t i v e phases of a c l e a n , s m o o t h AP o f t h e t y p e s h o w n . I t is only a s s i g n e d t o t h e AP s h a p e , a n d i s u s e d I r r e s p e c t i v e o f i t s b e i n g g e n e r a t e d by one or several fibers. The s p i k e v o l t a g e 1s a l s o c a l l e d p e a k - t o - p e a k a m p l i t u d e and the r i s e time peak-to-peak duration. From E k s t e d t ( 1 9 6 4 ) , p. 30.  dipole  generator  suspended  r e p r o d u c e AP's a s e n c o u n t e r e d p.  :  65).  the  This  comparison  i s no  handicap  generator record  simulate  the  remained  p o t e n t i a l a t a number  time  could  be  regained  velocity.  However,  (i)  SFP's  long  at  fixed  dividing  close  of the i n v e s t i g a t i o n  position points  the  are  of real  was  remain  (z,r).  very  be  The z  The  dipole  simultaneously  at a certain location.  whereas  distance  EMG.  velocity to  an e l e c t r o d e  e f f e c t s cannot  fibers  1969,  drawn.  s i g n a l with a  exactly  as t h e model p a r a m e t e r s  moved a t a g i v e n  of d i f f e r e n t by  As  purpose  the frequency behaviour  the frequency from  t h e main  c a n be  n o t be c o n v e n i e n t l y  dipole  s o l u t i o n does n o t  muscle ( s e e f o r example R o s e n f a l c k ,  results.  t h e AP a s a t i m e - v a r y i n g  Rather, the  could  i n an e l e c t r o l y t i c  since  conclusions  The model cannot  S i n g l e F i b e r Model  i n real  o f measurement  unchanged, r e l e v a n t  1 i  Spike duration  Limitations of the Laboratory A  Terminal Phases  by  the electode AP  "spiky".  as a f u n c t i o n  the  restored  sampled  AP  propagation  f o r two  They  of  reasons:  contain  main  9  frequency The  components  processes  which  are  frequency  (ii)  the  F i g . 1.4.  but  volume  Hence  the  account.  out  conductor  due  &  a  the f i b e r s  1969).  the  &  have  fiber)  were  stage  a  propagation and  also  cause  a  the  1978;  Stalberg  by  not  of  do n o t  spread take  hand.  dispersion data  the  be  more  1.1;  reduced can  near  propagasee  frequency considered  purely  (Schwan,  1957  &  is  Trontelj,  1979).  measurements,  shape  of  of  1963;  frequency  account.  the  of  resis&  into  the  of  AP  model  the  recorded  motorneuron  axons  innervation  sites  AP's.  I t means  that  the  individual  AP's  a l l at the  same t i m e .  The  duration.  The  fibers  arrive  resulting  With  the  i n both  muscle  from  i s not  the  dispersion  the  the  Eqn.  of the  taken  locations  so-called axis  of  affects  velocities  varying  same MU  further  could  recorded  decline  that  Therefore,  o f t h e model i n terms  elements  be  the  of  to  and  radial  could not  property  belonging to the is  effects  nature  tissue)  q u a s i - s t a t i o n a r y nature  another  fibers,  dependent  Stalberg,  frequency  different  this  (the muscle  T h e r e f o r e , the  (Gath  those  MUP  itself  contains frequency  perpendicular to  the  near  Yet  SFP's  strongly  1979)  interface,  e l e c t r o d e f o r the  according  has  Trontelj,  the  1979).  dependent.  However,  to  currents  far field  (Stalberg  conductor  of  muscle  of  potentials  into  "smoothed"  affected  volume  units  a plane  at  concentric needle  field,  in  model  are  Trontelj,  quasi-stationarily.  only the  muscle  on  taken  frequency  frequency  slightly  effect  the  are  limitations  also  the  be  of  &  electrode-electrolyte  2.4,  out  (StSlberg  Therefore the  Because  (along  carried  kHz  quasi-stationary.  dependent  the  the  spectrum  Plonsey,  and  at  fibers  also  tive  MUP:  taking place  not  of  The  Motor  10  dependence  tion  power  to  were  could  distant  up  discussed i n section  measurements  field  of  in  a  into storage  longer account on  tape  because or  disk  the and  10  computer-aided  signal  analysis  the dispersion  element  could  easily  be  intro-  duced.  1.4  EMG  Electrodes  The to  lead  free all  most  essential  o f f the desired  of d i s t o r t i o n .  quantity  Mechanically, them  apart  tioned at  a l l .  an (ii)  This  activity,  leading-off  interact  with  Otherwise "true"  discussed  t h e next  ability  activity) consistently  "universal"  must n o t c r u s h  electrode  can  fulfill  Damaged  fiber  fibers of  of the electrode  carry  irregular  t h e volume  a r e a l t e r e d because  i n turn  would  especially  surface  any f i b e r s b u t r a t h e r  surface  the properties  from  neither  give  lead  to a  because  rise  the  the needle  original  recorded when  no  AP's o r none i n the  of a disturbed  misinterpretation  t o t h e most  push  i s posi-  conductor  t h e muscle  fibers  ionic of the  closest  to  significant portion  of  and o t h e r  1.6  ideally  questions i n section  the concentric  needle  many  other  does  electrode  are treated  section,  EMG  nor the l e a d i n g - o f f  potential  signal  i n sections  system should  Those  cessing Apart  the  signal  amplifier K.  muscle  i s its  AP.  Electrically,  are  no  the leading-off  of a crushed  recorded  gross  electrode  criteria:  Moreover,  equilibrium.  that  the electrode  so that  o f a n EMG  ( S F P , MUP,  interstitially.  vicinity  the  property  I t i s obvious  mechanical and e l e c t r i c a l (i)  in  desirable  distribution  not  exactly  tissue.  correspond  to the  In addition,  have a t r a n s f e r concerning  should  i n the  i s i n the tissue.  a n d 2.4.  surface  Those  questions  the  electrode-  function  of pure  gain  signal  pro-  the e l e c t r i c a l  2.6.  electrode, electrodes  which exist.  i s described Each  one h a s  i n detail distinct  11  properties  r e l a t e d to  poses.  The  ties  a  of  priate  needle a  following paragraph few  a  small  reference The  EMG  electrodes.  the  More  in  because  consists  electrode  a  i s of  low  noise  area  the  conical  electrode  i s inexpensive  are  not  the  trouble.  I t provides  diameter  very  than  i n s u l a t i o n can  most  of  good a n t i - f r i c t i o n  Similar two  properties  fine  muscle  with  time.  Since  a  of  fine  wire  does  wander  fine  electrode  and  w i r e s where t h e  found  i n s u l a t e d wires  the  type  the  can  be  not  found  and  pur-  proper-  i n the  appro-  The  a  and  the  needle  i n t e r a c t with  recording traded  consistent break.  In  there  over  the  the  case  distortion.  EMG  very  increases  with  leadingattempts  because and  of the  two  which  of  its  because  of  consists  of  inserted into a  motion  studies.  characteristics,  i s made d i f f e r e n t i a l l y , f o r more  electrodes  They are  not  very  a l l  not  reshaping  comfort  tips.  wire  have  because  of  creating false  electrode  in kinesiological  elec-  coating.  can  i s useful  tool  tip  unrestricted pick-  surface  wire  remain  steel  the  subcutaneous  amplitudes  r e p a i r i n g or  Teflon  exposed  between  c h a r a c t e r i s t i c s are  good p a t i e n t  fine  stainless  searching  highest  and  does  a  sometimes b r e a k  i n the  with  s k i n or as  technique  occasionally  r e j e c t i o n are  of  a  leading-off  hypodermic  property  are  special  this  noise  various  construction  Its practically  rejection.  The  smaller  the  of  of  value  signal distortion.  surfaces.  can  the  insulated thin  I t y i e l d s the  of f  or  accordingly  s i g n a l i s recorded form  and  worth  an  The  use  one  serves  details  of  i n the  properties.  the  a l s o because  tip.  usually  needle  least  results  consistent  simply  electrode,  monopolar  and  radius  the  and  summarizes b r i e f l y  c o n i c a l bare  i t s omnidirectional  electrodes up  popular  monopolar needle  with  trode. of  ( i i ) above,  literature.  The  and  ( i ) and  long of  period  the  up  closely  reduced pickup  of  muscle,  Unfortunately,  picks  the  much  the  noise,  spaced radius  fine and  12  The the  bipolar concentric  regular  lumen  of  concentric  a  pickup  area,  between  picked  the  noise The  able  up.  I t i s done of  which  (about  1 mm)  a r e known.  only  directional  property.  tip  of the diameter  small  surface,  Single  much  fiber  contraction  with  MU's  recording  found i n Ekstedt  electrodes  many  require  not very  Usually  ratio.  Stilberg  than  which  improves  of  i n MU  considerterritory  surfaces, the are  quite  f o rthe patient. small  leading-off  Recording  resin  pickup  area  surface  i s made  i n a side port  as r e f e r e n c e .  This  concentric  o f a SFP even  Extensive  electrode information  near t h e  electrode.  strong  impedance about  between  configuration  needle  during  on  muscle  requires  SFEMG  a  c a n be  (1979).  concentric  either  signal,  low a m p l i t u d e s  the various  small  fiber.  The h i g h  electrode  small  & T r o n t e l j , 1979) a n d a p r o n o u n c e d  the bipolar  involved.  in a  the multielectrodes  by a v e r y  the recording  i s made  The  surfaces  comfortable  i n the  electrodes.  e x h i b i t s an e x t r e m e l y  of the bipolar  a second  results  i s useful  from  of  (1964) a n d S t a l b e r g & T r o n t e l j  the exception  ground e l e c t r o d e .  largest  and t h e needle  equipment.  which S/N  needle  i n i n s u l a t i n g epoxy  allow  Recording  as a ground e l e c t r o d e  o f a s i n g l e muscle  distortion  electrodes  quality  With  less  good  t h e same MUP  i s achieved  needle,  tip.  d i f f e r e n t i a t e d ) and o n l y  electrode  embedded  o f t h e hypodermic  introduces  high  This  a r e embedded  u p t o 14 l e a d i n g - o f f  The  o n e o r two f i b e r s ;  the  wires  t h e need f o r any f u r t h e r  and a r e t h e r e f o r e needle  at  hypodermic  by r e c o r d i n g  single fiber  order  a  fine  very  serves  with  of  Two  similar i n construction t o  electrodes,  and  The c a n n u l a u s u a l l y  (containing  this  center  property  the side  i s very  exposed  much d i s t o r t e d ( a l m o s t  along  spacings  the  two  needle multielectrode  studies.  The  those  and  r e j e c t i o n and e l i m i n a t e s  area  thick  electrode.  needle  directional  however, i s v e r y are  needle  hypodermic  differentially  needle electrode  needle  electrode,  a l l  EMG  as i n d i f f e r e n t / r e f e r e n c e o r as a  s k i n o r subcutaneous e l e c t r o d e s  serve  that  purpose.  13  Those  electrodes  muscle  1.5  AP's  The  type  Adrian  of  also end each  &  electrode steel  embedded  insulation the  i n motor n e r v e  (1929)  exposed  and  platinum  elliptical, constitutes application  so t h a t  the  needle  annular a  very the  insertion  the  of  observation  gross  EMG  of  compound  activity.  point  t i p should does n o t  1.6.  carefully  At  cause  The  the  tissue  concentric  15°  elliptical see  to the  of  inspected for  damage.  needle  electrode.  of  a  thin the  bare,  wire,  shaft  The  insertion. freedom  used  platinum  i s flush  F i g . 1.6.  ease  a  end  and  electrode  frequently  consists  distal  of about  promotes be  most  contains  which  cannula,  which  the  of  angle  and  been  It  resin.  insulation  concentric needle  today.  lumen  c u t a t an  the  i t has  e l e c t r o d e becomes  sharp  F1gure  and  until  the  epoxy  are  center  EMG  needle  insulating  the  for  introduced  measurements,  routine  hypodermic in  also  Electrode  Bronk  for  used  conduction tests  f o r electromyographic  stainless wire  occasionally  C o n c e n t r i c Needle  Since (CNE)  are  of  so  the that  with  the  bias  cut  Before "hooks"  14  The  dimensions 0.65  of a popular  diameter  of  mm  and  produces  t h e r e f o r e an  a  and c e n t e r  usually  h a s a l e n g t h o f 20  the  cannula  standard equipment.  are  DIN  wire  at  the  t o 60 to  mm.  the  other  1.7,  13L31, 13K58)  diameter  leading-off  surface  of of  At the proximal inner  end  provides  13K53  leads  a r e an o u t e r  0.15 150  are commercially  two  F i g . 1.7 d e p i c t s t h e DISA  FIqure  (DISA  e l e c t r o d e diameters  attached  jack  platinum  elliptic  cannula  CNE  mm. ym  The x 580  15° ym.  available.  The  end the c e n t r a l  of  a  connection  shielded to  CN e l e c t r o d e .  P h o t o g r a p h o f t h e DISA 13K53 concentric n e e d l e e l e c t r o d e ( s h a f t d i a m e t e r 0.45 nm).  the  cannula angle Other shaft  wire  and  cable.  A  measuring  15  Mainly  practical  technology clinical  exists  use.  mechanical  is  steel  tip  In addition, or other  hypodermic  needles  i s not affected  The b e v e l e d  (autoclave  can e a s i l y  by  that  saline  be r e g r o u n d  the stainless steel  sterilizing  o f t h e CNE.  The  a r e i n common and o f f e r s  good  t o ensure  con-  construction  a  i s easily  equipment).  T h e P r o b l e m o f CNEMG M e a s u r e m e n t Despite  the  Stainless  sharp p o i n t .  sterilizable  l e d t o t h e development  f o r manufacturing  rigidity.  sistently  1.6  considerations  i t s advantageous  mechanical  properties  and i t s  a p p l i c a t i o n o f t h e CNE i s l i m i t e d b y i t s d i s t o r t i o n s . usually  inserted  fibers  f o r highest  fibers  o f an a c t i v e  which The  contribute  number  fibers  tribute  1979).  MU v e r y  of those  close  i n section  f o r the study 1979).  close  1964).  t o any p a r t  to the "spike"  fibers  depends  on  of the leading-off  3.8.  t o the recorded o f MUP's  rather that  (Buchthal,  There  that  SFP's,  Ekstedt,  likely  Pt surface,  more  of the  o f t h e MU a r e  1 or 2 f i b e r s  than  t h e CNE d e f i n i t e l y i n clinical  EMG  not exactly 1964;  a l l of signal.  arrangement  Properties  of the several  of the recorded  the spatial  t h e CNE d o e s  1954;  a r e most  portion  o f t h e CNE  t o t h e axes  of the large  s i g n a l makes than  The s h a f t  parallel  surface.  The c i r c u m s t a n c e  I t i s known  i n t h e muscle  and t h e b e v e l  (Ekstedt,  significantly  significantly  Trontelj, signal  amplitude  i n the v i c i n i t y  discussed  trode  perpendicularly  t r a d i t i o n a l use,  The d i s t o r t i o n s c a n b a s i c a l l y be a t t r i b u t e d t o t h r e e  an e l e c -  (Stalberg  measure  Stalberg  con-  S  the true  & Trontelj,  f a c t o r s and t h e i r  interplay. (i)  The l a r g e , considerable led  off  section  elliptical  Pt leading-off  potential differences  has c o n t r i b u t i o n s 2.4).  Ekstedt  from &  area  o f 0.07 mm  i n the tissue.  a l l potentials  Stalberg  (1973)  2  encompasses  The s i g n a l t h a t i s  along  simulated  the surface on  a  (cf.  computer  16  the  isolated  effect  of  potential  averaging  of  the  elliptical  Pt  surface. (ii)  The p r e s e n c e  o f t h e CNE  distribution. and &  of  the  " s h u n t i n g o f volume Trontelj,  reports large  (iii)  Two  i n the tissue  1979)  about  and  also  the  cannula.  Ekstedt  The s i g n a l the  were  found  (1964)  shaft  w.r.t.  the cannula  distort  the  differential  Another  the  order  the  cannula  then  the  shape. of CNE  of  study  25%  to  that  zero potential (cf.  cancelled.  equal A  (Lundervold  of  different  signal  is  the cannula  3.8). on  the  wire  restricted  applications  (e.g.  from the  area  SFEMG)  to not appreciably  the core  in  both  i s not an i d e a l  pickup  and  I t i s generally  Ekstedt,  ('core') p o t e n t i a l .  distorted  and  of  Pt wire  L i , 1953;  shape than  Potentials core  effect"  reported cannula p o t e n t i a l s  the c e n t r a l  has a  &  more  but  a  amplitude  pickup  and  and  area  of the  fibers  are  are therefore  welcomed  i s  If  potential,  distant  cannula  is  in  reference electrode  i s responsible for a restricted  section  approximately  certain  30%  potential  fact  signal  enough  the  & L i (1953)  distorting  electrode.  i s low  ( B u c h t h a l , 1954)  differential  The  potential  (especially  between t h e c e n t r a l  ground  Stalberg  quantitative  Lundervold  obvious  effect"  1964;  No  o f t h e CNE  i n the l i t e r a t u r e .  a remote  that  2.4.  potential  ("wall  Ekstedt,  section  "no  the o r i g i n a l  distortion  of the presence  presumed  assumed  1964).  in  i s measured d i f f e r e n t i a l l y  cannula  of  currents";  explained  the e f f e c t s  cannula)  mechanisms  conductor  are  distorts  always  feature  for  traded  for  signals  are  distortions. The distorted  goal by  of  this  the  CNE.  investigation An  was  electrolytic  to tank  see  i n what  model  ways  offered  the  t h e most  practical  17  means  to  volume  that  conductor  m o d e l on  an  factors •  reach  a  for  the  mathematical  existed  (cf.  scale allowed  (iii),  point-shaped  fidelity  The  already  enlarged  ( i ) ..  goal.  in a static electrode  possible  ( true  quantification  the  section  recorded  value). the  Those  f o r an  1.2).  individual  environment. that  of  model  extracellular  The  realization  observation  The  elements  the  signals  measurements  distortions  AP  of  the  tested  introduced  by  the  of  a  the  distorting were:  with  served  in  the as  highest reference  CNE  or  parts  thereof. •  the as  elliptic field  disturbance  •  the  •  the presence  •  leading-off surface  insulator  the  signal  the  picked  aspects  of  averaging  ( i ) as  well  (ii).  surrounding of  f o r the  the  cannula up  by  as  the  core  to assess  a field  field  disturbances  disturbing factor  cannula,  distorting  the  (ii).  (ii).  differential  signal  (iii). The  main  features of  peak d u r a t i o n ,  spike  evaluation  of  the  whether  not  simple  or  an  duration; according  measurement  improvements  measures.  extracellular  of  Those matters  results. the are  CNE  AP  (peak-to-peak  t o F i g . 1.5) Finally,  amplitude,  served the  as  peak-to-  a basis  question  arose  for  the  as  to  r e c o r d i n g p r o p e r t i e s were p o s s i b l e  dealt with  in section  3.10.  by  18  Water, water, everywhere, And a l l t h e b o a r d s d i d s h r i n k ; Water, water, everywhere. Nor any drop to drink. Samuel T a y l o r (The A n c i e n t  II.  EXPERIMENTAL  APPARATUS  Coleridge  Mariner,  2)  19  The muscle  scale fiber  of  t h e model  becomes  were n o t u n w i e l d y . ly  easy  the  cannula  where  reasonably  large  model.  size  about  turned  stainless steel  (mm)  small  dimensions relative-  1:51.336 d u e t o t h e  f o r the construction of  sections  =  the  a p p a r a t u s were  tubing  and V  so t h a t  and tank  o u t t o be  i n the following  i n millimeters  1:50  but the electrode  scale  A l l dimensions  value  t o be  of the experimental  The a c t u a l  of a standard  £ = model  chosen  Thus a l l p a r t s  to construct.  availability  was  real  are given  value  as  %/V  i n micrometers  (um).  2.1  The M u s c l e The  St.)  dipole  welding  sponding muscle they  Fiber  be wires  see s e c t i o n  depicts  grooves  onto  1.2).  a  two s h o r t  1.5  was d r i l l e d mm  diameter  one o n t o  / 500 um a p a r t The n y l o n as  pieces  and l e n g t h  2a o f a s i n g l e  A hole  i n t h e tank  5 Minute  with  a diameter  soldered,  25.7 mm  the dipole  'Lepage'  having  1.2).  were  made  diameter  strung  onto the thread  guiding  was  r o d , each  (cf. section  insulated  2s,  model  t o t h e mean  could  Analog  each  fiber  o f 2.57 mm  axially nylon bead  was m o u n t e d  explained  / 50 um,  i n t o each  thread. that  Epoxy G l u e ;  correbrachii  "bead" so t h a t  Two  i n turn  thin were  braided epoxied  t o t h e mean d i p o l e onto  i n the next  a frame section.  model.  Two Component  steel ( s t .  i n t h e human b i c e p s  (corresponding  thread  of stainless  Boucherville,  Canada  1  length  fitting Figure  into 2.1  20  F i q u r e 2.1. The d i p o l e model .  2.2  The E l e c t r o l y t i c The  able The  tank  dimensions  t o represent walls  potential  of  depicted  to the wall. conductive  zero  when  determined  the tank  I f the walls  electrically voltage  were  so that  t h e tank  field.  perpendicular  Tank o f muscle  a p p e a r e d as an " u n l i m i t e d boundaries  which  are i n s u l a t o r s , then  In contrast,  w a l l which  the wall  by t h e area  volume  was d e s i r conductor".  the spread  of the  the i s o p o t e n t i a l lines are  isopotential lines  i s itself  i s grounded) .  limited  that  are parallel  an e q u i p o t e n t i a l s u r f a c e  Insulating walls  t o an  (assuming  made o u t o f  acrylic  21  Plexiglas®  were  transparent. insulators far  In  rather  lating  of  a  not  MU  tank  used  closer no  responded  be  of  of  (see  many  walls  than  were to  150  where of  -  in this an  electrolytic  tank  is  was  limited  to  necessary  to  measurements  must  of  field  of  about  volume  with  insu-  com-  zone"  unlimited  the  a  because  "buffer  an  represent  indicated that mm  to  electrode  not  to  are  relatively  a i r as  CNE  i t was  also  etc.  compared  the  the  liters  • • • 200  represent  shows t h e  reality  3.8)  hundred tank  made  in  s o l u t i o n with  1.6,  and  are  radius  sections  with  fat, skin  consideration,  the  uptake  work as  reality  tank  was  determined AP  as  by  the  dipole,  phase.  The  overall  length  of  (when t h e  "buffer  zones"  were  a  real  length  v e l o c i t y of  also  determined  the  spread  necessary  of  by  directional  the  there  record  a  7800  m/s.  The  behaviour  no  the  distor200  mm,  conductor  (see  nomenclature  p  AP's of  of  the  fiber in the  a CNE  tank  taken or  height  a  a  to  AP  and  800  as  mm  span of  depth  MU  r  of  the  done  positive  leaving 400  about the  z  »  mm  2 ms  tank,  or  part  at on  by  an the  This  thereof.  symmetrical, The  400 cor-  ( s e c t i o n 3.1).  model  cylindrically  Since  symmetrical  into account).  distance  simply  is  both  h e m i c y l i n d r i c a l area. was  duration.  record  was  time  possible was  maximum  extracellularly need  maximum r e c o r d i n g  single  the  was  about  cross-section  around  to  4  the  recorded  of  given  the  2.2  the  h a n d , were  of  the  preliminary  considered  other  only  the  under  represented  containing A  MU  to  such  boundaries  sux-face  Since  dipole-generated  propagation  the  practical  following description.  center  to  -  to  Figure  effectively  Since  less  measurements  length  negative  was  Those  The  w h o l e MU  muscle.  2.3).  the  a  even  biphasic  and  of  could  The  about  MU.  or  or  i n the  the  more  tank  When  section  even  vast  tions. the  conductors.  a  taken  material  d i r e c t i o n from the  or  fraction  be  AP  than  perpendicularly.  construct plete  SF  boundary  inserted only  a  The  a d d i t i o n , n a t u r a l muscle boundaries  away i n a r a d i a l  diameter  mm  chosen.  i t  was  measurement  turning  the  shaft  22  Figure 2 . 2 .  Photograph of the e l e c t r o l y t i c tank and tank n o m e n c l a t u r e ( b e l o w ) .  (above)  23  180°  around  back w a l l  i t s axis.  than  to  the  the  largest recording  the  tank  height  which  of  the  possible mounted  onto  fiber  could  center  of  2.3  recording given  the  growth o f  frame w i t h  20  ppm  The  first  the  saline  copper  obtained  since for  unlimited, tionally  a  to  » the  No  was  order  the  um  mm .  The  2  into  the  above and  fiber  The  actual  effectively. So  muscle  tank,  the  fiber  cf.  Fig.  positions  The  model  was  2.2.  The  w h i c h were  adjustable  allowed  values  a  used  series  in  for  the  Figure  fiber of  The  maximum  below, r e s p e c t i v e l y .  analog.  i n s e r t i o n depth  SL o f  0.9%  saline  algae  0.1%  =  275g o f  1980,  BDH  (Catalog  3  (=  the  second  was  negligible.  1.2  8g  cupric  a non-electrolyte  mho/m.  It  in  such  Rosenfalck and  shown  posi-  different  measurements  are  special of  20  Eqn.  effort to  was  22°C.  Chemicals  low  order  to  Ltd.,  SO^.  Poole,  5  H 0)  a f f e c t the  that  the  of  the  was  not  an  exact  (1969).  1.1. made The  The to  of  crucial muscle  The  that  tissue  potential  conductor  varies  conductivity keep  saline  the  can at  o  any  temperature  in  an  propor-  temperature  constant  remained  was  consider-  point  also  temperature  saline  value  vary  of  change  0.9%  inversely  is  added.  conductivity  concentration  Cg  England)  were  2  resulting conductivity very  prevent  n-Propyl p-hydroxybenzoate  d i d not a  In  The  i s o t r o p i c volume in  solution.  s u l f a t e Cu  and  effective conductivity  example  as  or CH  was  was  dependent. in  fungi  homogenous a,  of  effectively.  15.15  ym  (horizontally)  mm  /  3900  the to  200  1557  d.  depth  to  smallest  leaving  muscle  s u l f a t e CuSO^  whereas  was  and  275  2  chemical  see  y  from the  /  different vertical  electrode  CH .  2  solution  the  the  closer  3.1.  CH .  conductivity  /  zone  mm  f i t vertically  mm  about  placed  200  2  80  be  leaving  mm  three  could  measuring  centered  40,000 mm  at  contained  COO.  Then the  r was  600  which  and  bacteria,  and  ably,  was  variable  tank  fiber, analog  overall  also  arrangements  The  in  frame  in section  (OH).  was  frame  the  mm  anchored  the  and  distance  section  a  the  front wall.  600  tank  be  depicts  tion  was  cross  Thus,  very  which much  24  constant From  during  Glasstone  o was  ion  measurement  series  (1949) t h e f o l l o w i n g  but  could  temperature  vary  from  series  dependence o f the  to  series.  conductivity  developed  °l  where  one  -  T  dependent  / a  2  2  =  1  +  °  ( T  1  '  T  2  i s the temperature coefficient;  }  (  difference  a " 0.02  f o r NaCl.  of the e l e c t r o l y t e Hence  2  ,  i n °C a n d  a temperature  1  )  a an  variation  of  25  2°C  yielded  2.1  and  2.3  a  potential  In  order  on  to  the  sections Plotted where  1946  z  >  0,r  z  from  5%.  The  fiber in the  2*4  into  the  of the  the  of  CNE  similar  Figure  The  130  for mm  5%. would tank.  The  2.4  two  and  /  2530  curves  (r,z)  of  section  4%,  according  the  model.  actual  to  Eqns.  -I/4na] the  never  isopotential  line  1 m*  compare t o  80  mm  a  2.2.  when b o t h  above o r  the  No  r  plane  elecin  results.  clearly =  100  mm  worst to  the  be /  case be  (z,r)  measureable  f i b e r and  below the  results  quadrant  estimated  horizontal  Fig.  can  measured  was  Eqn.  described  first  exceeded  the  to  The  practical  walls  the  -  are  i n the  tank  area  in  and  in  computed  apparatus  that  obtained  according  The  theoretical  towards  conductor  tank measurements.  [in units  detected  volume  computed  Within  at  with  change  electrode  center.  Similarity i t was  s a t i s f i e d the  the  as  was  measurements  ym.  was  Physical  limited  lines  the  lines  position; 2.4  the  electrical  shows  were  positions  introduce  the  a l l later  question  of  distortions  theoretical  Fig.  set  and  isopotential  preceding tank  dimensions  electrode')  0.  of  isopotential  equivalent  i t s central  electrolytic error  the  the  Geometrical In  same  measured  results  were p u t  the  values =  properties  of  the >  the of  2.6.  only  and  deviation  in  and  Actual um  most  point  Properties  set  with  2.5  Tank  a  ('point  are  seen.  the  basis  used  the  verify  tank,  compared  trode  any  '  electrolytic  were  at  1.1.  V e r i f i c a t i o n of  1.1  variation  arose  shown  that  mathematical as  to  physically  model  whether similar  the  or  field (Eqn.  not  distribution 1.1)  with  a  in  the  maximum  the  scaled  up  version  of  distortions  i n the  geometrically  26  Z AXIS  Figure  (MICROMETERS)  2.4. The computed and p r a c t i c a l l y l i n e s , 1n u n i t s - I / 4 T T < J .  measured  isopotential  27  A  d e t a i l e d d e s c r i p t i o n of  the  electrochemical processes  trolyte  i n t e r f a c e would have exceeded the  body  literature  of  (1970).  More  (1976)  and  simpler wall  Weinmann  the  evidence  the  the  a  specific  metal,  was  In  1974  very  stainless  Au, of  the  and  metal The  electrode  approximation the  thesis.  electrodes  following  extent  for  which  that  the  metal-elec-  A  example  considerable  Bockris  is  found  paragraphs  i n t e r f a c e appears  geometrically  i m p e d a n c e was  discussed  as  there  interface  Reddy  in  Dymond  adress  an  was  &  the  insulating  already appears  some as  an  similar.  is  of  in  of  the  that  was  (or s a l i n e  specific  similar,  solution).  1971).  the  across  The  such  the  specific  i n t e r f a c e impedance  Z^  of the  portion  was  value  of  the  the  kind  of  as  interface,  resistivity  metals  point  etc.  i n t e r f a c e impedance  experimentally  much  from  with  distribution,  of  the  observed  gold,  same b e h a v i o u r .  namely  connection  interface  factors  to the  polarizable the  potential  Pollak,  the  in  However,  voltage  (1974c)  highly  2.6.  various  compared  essentially  very  to  (1971) s t a t e d t h a t  the  a l s o the  on  interest  metal-tissue  electrolyte,  steel,  of  original  (according  investigation, Pollak  exhibited  section  the  dependent  Pollak  of  mainly  infinitesimal  for stainless  tissue  be  an  Z^  impedance steel  an  i n F i g . 2.5  a,b).  high  concluded  Pt  shown  another  the  distortion of  impedance  electrode  be  as  concentration  (Pollak,  for  about  (1964).  To  will  set-up  as  -  electrode  circuit  important,  whether  possible  equivalent  exists,  the  Interface  overall  of  Mahler  1971).  field  measuring  view  information  &  this  electrochemistry  electrolyte  Metal-Tissue The  p.  of  (Pollak,  insulator,  The  specific  question  to  about  scope of  at  It of  l a r g e r than  that  platinum  could  the and  therefore  a l l three  the  tissue  metals  resistivity  p  28  ^  ^  ^ isopotential  \  \  electrolyte  lines  \ \  \  \ Vfs).  \ \  bpdr Zj  c Z{ dr  = s p e c i f i c impedance of the metal - t i s s u e I n t e r f a c e = r e s i s t i v i t y of t i s s u e = 1/<j = constants  p  b,c  metal  Figure  2.5,  Simplified equivalent tissue interface.  S h u n t i n g o f Volume C o n d u c t o r Along the i n t e r f a c e described  by  impedance. dipole  The  source.  resistances the  dipole  potential tion to  of  the  the  p of  metal  distortion tioned  through The  of  above,  original  Pollak  at  (1971,  the  from  interface  the  when  arise  volume  along  impedance  This  f o r a metal  increases  the  electrolyte,  surface. the  metal  V(s)  differences  which  specific  the  V(s)  anywhere  interface  If  of  potential  differences  bpdr.  the  bpdr  source.  resistivity via  The  S there are p o t e n t i a l  function  gradient  of  the  metal -  Currents  surface  the p o t e n t i a l  circuit  i t can  1974  the from  inside  Z^  the  puts  V(s). specific  over  the  A  2(cZ^dr)  over  the  from  therefore  larger  can bpdr  be  no  reduc-  parallel than  the  shunted  which  Fortunately, interface  be  to  driven  metal.  currents  v o l t a g e drop  the  and  i s n o t much  conductor  distribution  a,b,c) found  v o l t a g e drop are  can  interface  i s closer  currents  therefore  impedance  volume  surface the  which  infinite  i s a conductor  exist  infinity  diminishes the  potential  w i t h an  conductor  interface  differences  as  is a men-  impedances  29  to  be  tivity  very  p of the  In  order  impedances pared.  to  Z^  that  considered  verify  image"  f o r the metals  Au,  i t s description  Pt,,  related  statement  of  Pt,,  compared  and  the  very  to the bulk  high  a special  discussion  specific  test  of  the  to the shunting process  doubled resin  (1964) p o i n t e d o u t t h e s o - c a l l e d be  an  plane  of  potential  the  i s brought  source  at every  due  to  the  the  takes  place.  Ekstedt  very  small,  circular  "insulative  wall"  wall  genuine  into  on  resis-  interface  e l e c t r o d e was results,  two  preother  are explained.  the  volume  effect  insulator  (approaching  preceding paragraph.  be  of  the f u l l can  also  present)  <*>).  found  ym  Then  at  wall effect on  i f the  I t c a n be  a "less-than-perfeet* insulator)  Weber,  no  i n the case leading-off twice  the  f o r very  the  can  a  SF  does  not  that  "mirror  215).  The  i s therefore  "wall at  epoxy  effect"  a l l points  electrode with the  diameter  a  surrounding i n order  to  small recording distances. surface  itself  impedances  shunted  as  no  Z^ a r e v e r y  i n the  t o be a n  insula-  some s h u n t i n g  completely  (with  explained  e l e c t r o d e t h e r e f o r e appears expected  p.  be  large  insulating  surface  interface  be  1950,  doubling  fiber  leading-off  specific  electrical  The  o f an  can  infinitely  such  exact  tissue  boundary  field.  produces  The  an an  electrolyte  a n d image  currents  The m e t a l l i c  i n the e l e c t r o l y t e .  that  least  occur  -  size,  diameter  no  conductor,  surface  insulator  25  When  ( s e e f o r example  leading-off  (1964)  "wall effect".  conductor.  the i n s u l a t o r  finite  must  approximately A  volume  i s produced  point  surrounding  exert  unlimited  by t h e s u p e r p o s i t i o n o f t h e r e a l  although  is  Pollak's  are closely  to  insulating  tor  Au,  Effect Ekstedt  large  f o r the metals  electrolyte.  Before  effects  Wall  large  suppress  (when t h e this  metal  "metallic  30  wall  effect".  Also,  recording  distance  Potential  Averaging  The  the  separately  but  into  the  amplifier.  V  V(s)  along  surface  =  !  e  Both, w a l l the  model  V(s)  effect  because  can  q  V(s) the  be  and  the  of  the  along  the  potential V  to  leading-off  which the  on  e  Pollak  surface  potential is  interface  a p p r o x i m a t e d by  S according  / S  s  only  shape  f a c t o r by  distribution  measured  V  and  determine the  potential  the  size  the  the  S  which  average of  the  increased.  surface  metal,  and  the  cannot  be  is led off potentials  (1971)  ds  (2.2)  p o t e n t i a l averaging  take place  potential distribution  V(s)  is  according  to  geometrically  scale  in  similar  to  reality.  Verification In effect  Measurements  order and  elliptic  to  measure  averaging,  acrylic  a  glass  small  circular  flush  with  acrylic  / CNE of  150  um  under the  tions  the x  580  ym  3.1  nomenclature).  for  relative  surface  {=  leading-off glass.  amplitude  These  pure area  The  corresponding  the  importance  special electrode  i n v e s t i g a t i o n ; see  peak-to-peak 2.6,  the  vs.  insulator) 0.8  mm  ellipse  had  the  the  size  section the  description measurements  of  2.5.  recording of  the  took  shunting  constructed.  of  to  also  was  of  center  15  urn d i a m e t e r  dimensions  7.7  leading-off  Then  a  distance  account  series r  was  of was  mm  of  of  an a  ground  x 29.8 of  mm the  measurements  made  the  wall  which  surface  apparatus only  to  consisted  the  electrical into  It  in  /  the  compared  (cf.  plus  sec-  general  "pure  wall  31  effect"  arising  recording  distance  Then  elliptical  size  was  series  the with  still  surface  a small  exposed  averaged  hole  Any  see  interface  with  neither  illustrated from  the  The p o i n t  shunting  that  reported  t o have  impedance. shunting,  curves  electrode tor)  effect  the and  2.6 c o m p a r e s  are plotted  t h e same  that  o f t h e CNE  the Pt f o i l . the wall  o f volume For  The  'core'  impedance  electrode  wall  conductor  comparison,  the point-  (for a description,  differed  electrode  amplitude  2.3  i t was  by a t most  was  Au  (Pollak,  were  1974c), i t  t h e same s p e c i f i c  incorporated  5%  plated  Au, P t a n d s t . s t .  behaviour  A  effect  t o t h e "pure  ( i n section  i n the tank  same  leading-off  the true peak-to-peak  nor averaging  the  interface  a l l distortions  -  averaging. a l l r e s u l t s o f t h e measurements  i n % o f the peak-to-peak  = 100%) v s . t h e r e c o r d i n g  reveals  alone  also possessed  'core*  from  small  the wall  of  the s t . s t .  of Pt.  p o l a r i z a b l e metals  Au, P t o r s t . s t .  Therefore  Figure  the highly  essentially  that  wall  effect  Z^  than  foil  vs. r) yielded  recorded  distribution).  2.5) b u t s i n c e  Pt  the  potential  v s . r w e r e a l s o made w i t h  the p o t e n t i a l d i s t r i b u t i o n  (section  a  so t h a t  impedances  'core'  small  distortion  with  of  the extremely  i n p o t e n t i a l compared  electrode  nor wall  theoretical  was c o n c l u d e d  covered  amplitude  function  negligibly  any o t h e r  amplitude  a  that  t o be a t t r i b u t e d t o s h u n t i n g  and the e l l i p t i c  section 2.5).  a  i n the center  decrease  have  the specific  electrode  assumed  as  to the e l e c t r o l y t e but i s o l a t e d  measurements o f t h e p e a k - t o - p e a k shaped  be  surface,  only  was  (peak-to-peak  p o t e n t i a l would by  safely  electrode  the "insulator Pt".  currents  acrylic  d i d not introduce  same  o f measurements  effect"  elliptic  I t could  and t h e r e f o r e  effect.  surface  the  r.  leading-off  difference  of  from  the f u l l  factor  distance of 2  amplitude r.  from  described  of the true  The t o p c u r v e  t h e "pure  wall  above. value  (genuine effect"  The  (point insula-  was  only  32  io H  1  1  '  '  0  I  '  200  1  '  1  1  400  '  '  1  '  1  600  RECORDING  Figure  2.6.  The PTPA vs r •averaging" and t r u e PTPA.  1  1  1  800  1  1  1  1  1000  DISTANCE  R  r  1  1  1  •  1200  1  1  1  >  i  1400  (MICROMETERS!  for "shunting", "wall their combinations. In  effect". % of the  1  ,  1600  ,  ,  1  180  33  e x e r t e d where r  < 50  for  the  r  > 800  second  um  curve  insulator  maximum  1.57  at  decrease  effect".  The  which  The  for  the  a l l  averaging.  The  less  than  of  the  was  at  3.1)  the  by  curves  distortions  the  smallest  potential  wall  increase  potential  averaging,  not  potential  be  a  at  r  factor  genuine  The  only  the  compared less  than  the  wall to  also  50%  shunting  of  200  100%. It  shunting  and  for  also  in  >  shown.  r  >  25  allowed  combined"  shown  a  wall  for r  line  of  to  "pure  10%  effect,  roughly  also  The  a factor  the  base  is  and  "less-than-  by  to  measurements  and  are  shunting  to on  a  much  ever  Pt or  was Au  35%  or  Fig.  um the  "pure  2.6,  um  had  and the  surrounding  22%  a  the  only  r  =  about  200  200  were  um, 20%  the  ym) . and  similarity  demonstrated cf.  and  always  effect  section  less  than  counteracted  potential  (99%  Also,  the  wall  effect  than  shunting  "pure" but (67%  um).  shunting (epoxy  2.6  48.7  shunting  at r =  core  =  i n f l u e n c e on  of  of  Figure (r  stronger  effect  geometrical  s u r f a c e was  at  independent  separately,  used  stronger  and  f o r the  process.  shunting  the  um  was  48.7  concern  distance  due  deemphasizes  insulator  amounted  which  the  48.7  which  to  um  corresponding  electrode  due  the  potential  below  150  curves.  had =  at r =  'core'  r =  increase.  with  3.1)  was  curve  at  potential  section  shunting  pm.  1.5  measured  shunting,  first  350  Shunting  measured  decrease  Another has  >  was  which  to  Au  curves,  decrease  effect  by  decrease  recording  ym.  in  f o r ' "averaging  Those  potential  could  r  the measured  w h e r e r > 200 the  potential  was  10%  increased the  distortions  a l r e a d y mentioned,  model  that  10%  from  due  i n the  potential  the  alone.  caused  down t o  than  100%  remark  elliptic  where  averaging" calculated  shown  less  of  (see 22%  rapidly  effect  decrease  10%  of  wall  about  fell  caused  line  um  whole  net  extraction  As  •*• 25  potential  incorporates  and  The  is explicitly  curve  base  Pt".  of  factor  effect  the  r  potential  The  wall  above  perfect  um  ym.  further.  resin,  The  CNE  cf. section  also 1.5).  34  As  mentioned p r e v i o u s l y , a w a l l e f f e c t  area  of  at  least  pronounced alone.  than  'core'  to  3.4  are  Thus, along  the  distortions  2.5  concluded  o r Au  amounts  to  'core'  curve  was  for  the  that  due  area,  i s t h e r e f o r e much  from  only  and the  along  less  not  Pt  the  calculated  'core*  and  Pt  but  'core  &  as  a  an  more  So  the  percentage  insulator i n the  has  surface  surface.  expressed by  which  leading-off  the  when  surrounded  to  the  l e a d i n g - o f f s u r f a c e s the  in a geometrically similar  following  experimental  than  sections  insulation'  CNE  with 3.2 sub-  relative  m o d e l CNE  fashion to  unimportance correctly  of  shunting  represented  the  reality.  simple  •  high  •  good s t a b i l i t y  •  ease of  •  must p r o v i d e  Fig.  a  requirements  the  nature  of  the  various  manufacturing;  2.7  and  sturdiness;  installation  an  (mechanically/electrically);  reproducible  electrode  cylindrical  results.  holder shaft  is of  self-centered,  tions.  The  electrode holder  axis  two  sturdy  aluminum  had  shown the  a g a i n s t a V-shaped opening  vertically  on  determined  accuracy;  The  pressed  design  electrodes:  •  ments.  in  effect"  insulator,  Electrodes The  In  results  core  place  the  exact  the  from t h a t  presented.  i t was Pt  takes  shunting  The  of wall  measured with  combined  assemblies  "metallic  by  alone.  the  that  however,  decrease  the p o t e n t i a l  the  times  the  Shunting,  potential of  10  arises  by  rails.  means o f  of  the  with  weight  of  two  electrode  consecutive  which  require-  diameters,  Thus the  for  the  last  various  a screw.  position  runners The  fulfills  electrodes,  identical two  that  i t slid  was was  installa-  along  the  electrode produced  zthe  35  necessary runners V2"  friction  e i t h e r end  in place.  t h i c k p l e x i g l a s tank w a l l s .  Figure  2.8  with  allowed  y/d.  I t was 0.5  1  the  mm  divisions  that  mm  ym  because  /  on  p o s i t i o n i n g of  estimated  recording  possible  on  the  shows t h e  The  rails  in turn  had  m i l l e d upper  edge o f  the  complete  electrode  posi-  assembly.  parts  small  firmly r-axis  most  which  assembly i n the  Rulers  at  the  slid  tioning  at  to hold  9.7  of  a high  the  r  the  field  fixed  parts  electrode  for a l l three  occurred.  distances  the  axes  I t was, electrode  gradient.  in z,  of be The  and  the  r , y/d course,  marks  on  coordinate  the  z,  r,  a positioning error  of  very  system  mobile  crucial  positioned  as  transparency  of  that  precisely the  tank  for as  walls  36  F igure  proved and  t o be p r a c t i c a l  corrected  Electrode  This  electrode  consisted mm  i n that  The c o m p l e t e  positioning  the electrode  assembly.  p o s i t i o n could  be  checked  visually  mentioned  earlier.  i f necessary.  The P o i n t  It  2.8.  of a  about  1.27  /  point  electrode.  25  was  Teflon um  used  f o r reference  insulated  long  and t h i c k .  measurements welding  Figure  2.9  as  rod with shows  a  c o n i c a l bare t i p  the d i s t a l  end of the  37  Figure  The P o i n t  Electrode  Figure  2.10  measurements of  plexiglas,  of  the sheet,  with  tion  shows  an  2.4.  was No  this  a small  then  special  circular  connected  modified  diameter  electrode.  was  made  o f 95 mm ( 0 . 8 mm  /  used  1850  / 15  V"  ym)  as  (the a c r y l i c  x 29.8 nun) i s s h o w n .  effect  thick  8  ym.  In the  was  welding  measurements  electrode  for wall  from a  insulated thin  f o r the s p e c i a l  s h a p e o f 7.7 mm  which  I t was  surface  t o an  p i c t u r e of the modified  down t o a n e l l i p t i c  design  i n s e c t i o n 3.2.  approximate  t h e p l e x i g l a s and  electrode  The p o i n t - s h a p e d  S u r r o u n d e d by an " I n s u l a t i n g W a l l "  as p r e s e n t e d with  2.9.  sheet center  ground  rod.  The  described sheet  flush  was  in  same sec-  milled  38  F i g u r e 2.10.  Development o f Each  the  CN  E l e c t r o d e Model  complete  CN  e l e c t r o d e has  wire,  or  nula,  surrounding  assess trode  'core',  the  The point electrode * i nsu1 a t i ng wa11 " .  the  insulating  both  individual  sub-assemblies second  core  and  epoxy  the  core,  the  was  the  third  corresponded  in  to  a  from  complete  a  complete  insulation  The core  first  the  and  electrode.  In  assembly  with  an  core,  and  surrounded  electrode  by  c o n s t i t u e n t s ; the  surrounding  the  core,  constructed. formed  fundamental  resin  resin  p r o p e r t i e s of were  three  surrounded  by a  cannula,  central the  can-  order  three  elec-  consisted solely i t s insulator,  cannula  to  of  while  surrounding  an  39  insulated  core.  A l l three  assemblies  were  separately  available  for  measure-  ments .  'Core* The  core  2  c u t t i p became  axis  mm  Au  29.8  3  the  /  with  which  t i p was  methanol.  The  elliptical  &  deemed m o s t  exhibited 'core'  'KryIon'Enamel  Matthey  with  The  Au p l a t e d  Cathodical  580  elliptical  ym.  was  essentially  3  o f a n i n s u l a t e d , 7.7  obliquely  cleaned  2  consisted  the  same  / 150 axis  with  surface  7.7  mm  /  brass 150  f i n e sandpaper  received  In s e c t i o n  impedance  ym t h i c k  2.4  behaviour  a  thin  i t was  as  Pt.  ym  r o d whose and  major  and c a r e f u l l y  layer of  concluded Figure  plated that  2.11  Au  shows  electrode.  spray p a i n t ,  Borden  e l e c t r o p l a t i n g with Mallory  minor  polished  practical.  mm  Products  'acid hard  Ltd., Montreal,  Canada)  L t d . , Cobourg, gold  Canada.  plating solution'  a t about  1 t o 2 mA/cm  (by 2  Johnson  f o r /2 X  h.  40  •Core s  Insulation'  Figure consisted the  of  elliptic  Au p l a t e d  2.12 a  (right) 25.4  mm  depicts  / 494  ym  insulation surface  as o u t l i n e d  i n footnote  the core  with  diameter  acrylic  became 3.  98.1  mm  the surrounding  /  rod. 1910  Thus ym.  insulation  the major The  brass  that  axis core  of was  41  F i g u r e 2.12.  Complete A  outer  26.6 mm  diameter  insulation' sharpened plete  (right)  and the  Electrode  stainless  diameter  The 'core & I n s u l a t i o n ' c o m p l e t e CNE ( l e f t ) .  steel  tubing,  / 518 ym,  was m i l l e d  of the annular  assembly  to a point  was  outer  glued  of about  33.4  mm  down t o a n a n g l e  ellipse into  diameter  became  129 mm  the cannula.  50° a c c o r d i n g  e l e c t r o d e i s p i c t u r e d i n F i g . 2.12  650  ym  and  inner  o f 15° s o t h a t t h e l o n g /  2510  The d i s t a l  t o DISA  (left).  /  ym.  A  cannula  specifications.  'core  and  t i p was T h e com-  42  Table popular  2.1 s u m m a r i z e s  a n d compares  C N E ' s , DISA 1 3 L 3 1 ,  T A B L E 2.1  t h e dimensions  cannula  inner  "  center  D i m e n s i o n s o f t h e m o d e l a n d r e a l CNE.  "  The  650  "  "  Reference The  dia.  electrode  CNE a n d two  13K58.  DISA outer  o f t h e model  13L31/13K58 Mm  N/A dia.  150  ym  area  150 =  um x 580 um 0.07 mm  Model 33.4  mm/650 ym  26.6  mm/518 ym  7.7  mm/150 ym  7.7 mm x 29.8 mm = 180.2 mm /0.07  2  2  mm  2  Electrode  reference,  indifferent  o r ground  electrode  ideally  satisfies  two c o n -  ditions: (i)  i t i s s o f a r away  from  the biological  generator  that  i t assumes  zero  potential; (ii)  i t has a large  Various fulfilled. tank the a  configurations  the electrode  generator,  large reference  The  reference  interference sisted the  surface  electrode  over area  tested.  electrode  surface  surface  design,  its full of roughly  length  spanned  close  which  t o zero  was a l s o  (i) could  was a s s u m e d .  fulfilled  i n Fig.  laying This  The c o n n e c t i o n  volume  o f "symmetric"  influenced  i s sketched  not directly  a considerable  a kind  i nturn  welding rod  70 c m .  low impedance.  Obviously  o f 800 mm. 2  a very  assumed  which  t h e environment,  o f a 3 mm d i a m e t e r  tank  with  then a p o t e n t i a l  electrode from  area  were  I f the reference  so that dipole  contact  of  be the  position to That  implied  ( i i ) automatically. by t e s t s  2.13.  about  I t simply  i n t h e lower back  corresponded t o t h e bare  con-  corner o f  t o a very  noise  large  reference  43  rod  electrode  welded  to  was  i t .  symmetrical  made  The  with  an  insulation  arrangement  of  the  insulated smaller of  the  latter  reference  was  rod  that  important  electrode  as  well  to  as  to  was  point-  preserve reduce  the noise  interference.  insulated  st. st. rod  800  FIgure  Treatment of  the  Various all  of  Leading-off  techniques  which  aim  improving  the  cleaning"  Stilberg  "presoaking chloriding"  in  2 .13.  at  a  &  have  been  proposed  the  of  et  the  al.  as p r o p o s e d by  leading-off  of  techniques  "electrolytic  Wiechers  both  treat  impedance  Such  (1979),  agent"  or a combination  electrode.  to  overall  stability.  Trontelj  wetting  reference  Surface  reducing  interface  The  mm  the  electrode  include  etching"  (1979), various  "Pt  surface, and  at  "electrolytic  Pollak  (1974c),  black"  and  authors.  "Ag  44  Since  the  large  contact  Before  each  methanol  to  model e l e c t r o d e impedances area  ( c f . 2.6),  none  measurement  series,  remove  and  fat  of  the  dirt  were  those  i n any  special  core  and/or  which  could  case  very  treatments cannula  build  up  low  due  was  necessary.  was  to  cleaned  from  the  with  handling  the  electrodes.  2.6  Electrical  Dipole  Source  As  Apparatus  Generator  presented  constant  current  however,  a  and  during  the  the  Higher 2.4)  the  slowly  to  a  can  be  signal  The  measurement  decrease generator  due  t h a t the  a  A  1  in  squarewave  A  sinewave  would  of  was  resulted  parallel  In  achieve to at  as  with  showed  t o s h u n t i n g was  a t most  22%  for r =  the  interface  for  that 48.7  deemed a p p r o p r i a t e .  unsuitable interface amplitude  The the  shunting  at vnn.  1  frequency  square  kHz  wave  distortions. (cf.  section  impedance  example  a  balanced  the  chosen.  occur  ' see  a  be  as  practice,  Accurate  was  specific  circuit;  modeled  i n strong non-linear  2.4  was  to  occurred  increased  dependence o f the  be  fiber.  observed  1 kHz  section  1 kHz  the  order  d i d not  have  can  distorted.  in  current of  fiber  along  used  same p r o b l e m  kHz  RC  results  be  strongly  amplitude  frequency  as  active  travelling  must  was  impossible.  than  an  part, non-linear processes  changing  simplified  source  dipole.  "flat"  frequencies  due  introduction,  source  the  l a r g e enough so  where  AC  in  were  the  dipole  recorded  measurements was  DC  constant  charge-transfer because  in  Pollak, the  Therefore  Z^  (Z^  1974a).  potential a  sinewave  45  The  Current The  T£  Source  constant  /  current source  as  shown  positive  i n Appendix  for  both  and  R3/R3' »  T h e c u r r e n t was  Tj/  T j ' with  t h e op-amps  function R2  /  adjustment drifts  variation hand. since nor  was  balance  special  produced  value  a very  The  control  voltage.  effort  was  collector-emitter  by c o n t r o l l i n g  input  signal  from  via resistive  of the function  generator  imbalance  t o keep  neither affected  was  123A*  VCF  dividers  ,  allowed  a  interface.  probably  fine Small  d u e t o some  corrected periodically  the balance  t h e RMS  voltage  currents of  •EXACT  voltage  long periods of time,  The  made  value  measured w i t h  the various electrodes.  stable  amplitude  output  an  T^,  current  supply  t h e base  a t the electrode-electrolyte  occurred over  Darlingtons  given by t h e s t a b i l i z e d  constant  OP^/OP^'.  balance  t h e s m a l l DC d r i f t  t h e RMS  held  The D C - o f f s e t  of the supply  No  T h e maximum  f e d t o t h e op-amps  o f the charge  i n this  1,  a n d n e g a t i v e p h a s e was  generator  Rj', R2'»  c o n s i s t e d o f two c o m p l e m e n t a r y  electronically of the current The f u n c t i o n  and frequency.  The o u t p u t  by  stable injected  generator current  I Si  was p e r i o d i c a l l y out  a l l measurements,  high not be  m e a s u r e d b y means  amplitudes too large  noted  that  difference  a  was  i n the order  amplitudes a  metal-electrolyte linearly,  I  measured w i t h  30.5 mA  potential  RMS  o f 1 mV  up t o a b o u t  600 mV  influences  Pollak  the interface  the e l e c t r o d e .  sinusoidal.  f a r away  difference  interface  see f o r example across  o f t h e s m a l l shunt  of  more  the f i b e r  than  specific  Plonsey  i s not measurable  8.2  This yielded  a t r = 2.5 mm  the  (1974a),  from  resistor  100  interface  (1969).  sufficiently  um. mV  across  impedance  than  and  I t should  The t r u e  but smaller  Through-  ( r » 100 mm)  / 48.7  about  ft.  the non-  potential  the voltage  46  The time.  two  small  The c o n s i d e r a b l e  that  l e d to a buildup  beads  of the dipole  current  density  h a d t o be  o f about  of reaction products,  cleaned  150 mA/cm  probably  iron  from  induced  2  oxides  time  to  reactions  and/or  copper  from t h e copper s u l f a t e .  The  Measuring Three (i)  Set-up  aspects As  were i m p o r t a n t  l i t t l e  and  current  amplifier  electrolyte. potential voltage  V  i  as p o s s i b l e  to prevent This  c a n be a c h i e v e d  g  through  the  small, (ii)  The  c f .section  input  impedance  the (iii)  however  small  roll-off  interest,  i  by  (Z^Z^)  t h e volume  >>>  R^'.  V  i n the  g  The a v e r a g e d  as t h e voltage  conductor  of a  current  of the e l e c t r o l y t e .  the specific  &  >>  Z  1974a).  impedance  of i  e  the electrode  of the p o t e n t i a l source  the amplifier Z  a m p l i f i e r impedance  The s i g n a l p a t h  the  of  Pollak,  the electrode  through  The  i  s  .  current  i n t o t h e a m p l i f i e r must n o t be m i s t a k e n a s  when  impedance, Z^;  flow  i n t e r f a c e impedances  Z^ a r e  2.4.  impedance  electrode  over  currents  should  resistances  the electrode  shunted  m e a s u r e m e n t s ; c f . F i g . 2.14:  i s represented  R,/R, ' f e d b y b b  Rj^/R^' a r e t h e e f f e c t i v e i  loading  at the electrode  e  divider  3  f o r accurate  Z  g  g  must  be  (simplified Then o n l y  while  much  the f u l l  value  frequencies  are  i fpossible, or that  C  a  , R  outside the linear  a  of  drops  drops  over  and measured. dependent  should  the  of  the  electrode  a n e g l i g i b l e voltage  c o n s t i t u t e s a frequency  i s l The elements  than  equivalent  Z , where i t i s a m p l i f i e d  g  higher  impedance,  be c h o s e n  frequency  d i s t o r t i o n s remain  so t h a t  band  of  minimal.  47  The  transfer  function R  G  (  =  V /V i s given - a -e  e  Pollak  electrodes  T w h e r e  2.14.  (1974b, p . were a s s u m e d  R  e  +R  6 T  a  T*  From  1  1+jojT  F T R " • 1+535?  FIgure  by  T  - V  a  R  a a  (2.3)  + a  a  = R C  R  +R  The e q u i v a l e n t c i r c u i t of the electrolyte, e l e c t r o d e and a m p l i f i e r Impedances.  463)  the  following  (at 1 kHz):  realistic  impedance  values  f o r Pt  48  •  real  electrode  -70°;  this  with  gave  0.07 R  mm  leading-off surface  2  »  300  k i l l |C  *  e •  model  electrode  -30"; A  this  180  c r u d e measurement o f  « 400.,  mm  ,  « 2  pF,  mm):  »  4.4  7.5  mm)  T  = x  lO^fi,  10" *  s;  1  T  « 9  g  x 10"  (D =  :  Z —e  =  40fl,  s.  5  the  model e l e c t r o d e  confirmed  the  ( 1 9 8 0 ) , an  amplifier input  impedance  Z  above v a l u e  of  Z -e  || 200  pF  -30°.  From R e i n e r  a Rogoff  —  (including ative  0.3  e  leading-off surface  2  « 46ft| ICT  q  nF  e  with  gave R  1.5  (D =  shield  capacitance  of  cable)  s i d e , f o r a modern m e a s u r i n g  seemed  system.  justified,  This  gave T  « 100  MP,  cL  t o be » 0.02  on  the  s at  conserv-  1  kHz.  ct  Thus f o r the frequencies to  an  320  real  Hz  amplitude  e l e c t r o d e , T*  and  360  Hz  attenuation  « 5  there  of  x 10 *  s.  slope  of  _t  is a  about  -1  dB.  This -20  means t h a t b e t w e e n  db/decade,  Otherwise,  the  the  corresponding  frequency  response  is f l a t . T h e r e i s an a d d i t i o n a l , frequency independent,attenuation of R / ( R +R ) = 0.997 = -0.026 dB. A h i g h e r a m p l i f i e r i n p u t r e s i s t a n c e or a lower a e a ^ input  capacitance  Special  techniques  capacitance, The  above  possible  would have  such  as  numerical  frequency  different  result been  driven  are  a  for of  smaller  developed  shield  example  response  results  in  a  the  obtained  frequency  by  circuitry real  others or  a  electrode  other  to  was  attenuation.  reduce  negative  transfer function for  dependent  given  the  input to  or  impedance.  illustrate  G(ju>) i n E q n .  electrodes  input  2.3.  other  a  Much  amplifier  specifications. For  the  model  impedance  values,  Also,  to  three  due  R  a  electrode, T*  /(R  e  « T +R  a  q  was  ) « 0,  p r e v i o u s l y mentioned  no  frequency  problems  obtained.  So  no  attenuation  overall  conditions  ( i ) ..  there  occurred.  was  no  frequency  occurred.  ( i i i ) were  With  the  dependence.  Therefore,  satisfied.  given  a l l  49  The  Amplifier A  differential  rejection  was  consisted  of  converting Pj  /Pj'*  R^  /P  T n  output  constructed. a  e  op-amps  resistors  gain  voltage  could was  Pg  the  be  complete  differential  had  an  For  10  the  ponents  It  Each  voltage The  Appendix  inputs  an  common mode  2.  It  basically impedance  were  driven  by  adjustable  offset  voltage  f o r the  input  i t s nominal  bias  currents  value  was  and  with with  s e t t o .5.  The  R  II  P  2  gain  -* *> 2  of  !•>  OP2,  input  which  Practically in  impedance  range  true  with  and  RMS  a  was  theoretically  obtained  the  values  order  of  80  ( s e v e r a l hundred  'FLUKE 8012  frequency  feature  made  from e l e c t r o d e p o t e n t i a l s or  mainly  had  finely;  a m p l i f i e r were  high  whose  in  and  3 + 3'  CMR.  measured  amplifier.  recorded  OP^  appears  impedance  of  dB. M")  one, the  CMR  The  FET  and  could  input  of  be the  op-amps currents  pA.  _ was out  digits.  the  maximum  extremely  of only  V  a  op-amp  input  by  differential  to  high  circuit  adjusted  R^  v  adjusted  very  R^/R^' c o m p e n s a t e d  given  out  a  OPj/OPj'.  R  With  The  differential  FET  the  2  a m p l i f i e r with  served signal.  used throughout  v  w o  as  u  a  s  t  also  a monitoring Figure  2.15  used,  offset on  instrument  the i n v e s t i g a t i o n .  digital ^  the  a  and a  multimeter  accuracy  i t unnecessary  observed  shows  A*  was  to  ±  0.5%  block  temperature  for true  of  off  drift  RMS.  reading any  +2  DC  com-  voltages  from  'TEKTRONIX T935 A' o s c i l l o s c o p e .  to  picture  detect of  the  any  irregularities  electrical  in  apparatus  the as  50  F i g u r e 2.15. P h o t o g r a p h o f t h e e l e c t r i c a l  apparatus.  Miscellaneous Shielded order  cables  t o reduce  remove  noise  electrical  connection addition, absolutely  was  used  between  interference.  equipment  made  proper  were  to  from  of  and t h e a m p l i f i e r  Special precaution  t h e immediate  t h e mains  grounding  the electrodes  of  equipment  the reference  vicinity  was  only  taken  o f the tank  other  than  electrode  and  in  as t o a n d no  necessary. the  shields  In was  necessary.  Special  care  h a d t o be  taken  to avoid  common g r o u n d o f t h e d i p o l e g e n e r a t o r  undesired  and t h e measuring  current circuit.  flow  through  a  Therefore the  51  power supply -  generator The  sketch  rents a  f o r t h e two h a d t o b e c o m p l e t e l y  s i d e was s e p a r a t e d i n Appendix  i n the case  common  cannula  mode  3 shows  t h e mains by a c o n s t a n t  t h e pathways  o f n o n - i s o l a t e d power  voltage  V_ . g e n e r a t e d CM  i n the d i f f e r e n t i a l  therefore  from  essential.  isolated.  measurement  (dotted lines)  supplies.  voltage  A high  the  transformer.  o f t h e unwanted  The c i r c u i t  by t h e d i p o l e ,  mode.  F o r convenience,  also  shows  curthat  occurred a t t h e core and  CMR  of the amplifier  was  52  For out of olde feldes, a s men seith, C o m e t h a l l t h i s newe c o r n f r o m y e r e t o y e r e } And out of olde bokes, i n good feith, Cometh a l l t h i s newe s c i e n c e t h a t men l e r e .  (The  III.  RESULTS AND  DISCUSSION  G e o f f r e y Chaucer P a r l i a m e n t o f Fowls)  53  3.1  General For  Remarks  a l l  n o m e n c l a t u r e was  Recording  used;  Distance  T h i s was center  measurements  see a l s o  this  investigation  the  following  F i g . 2.2.  r  t h e d i s t a n c e b e t w e e n t h e two p a r a l l e l  o f the° c o r e  recording  throughout  and t h e c e n t e r  d i s t a n c e was  varied  F Ipjure 3 . 1 .  of the f i b e r ,  b e t w e e n r = 2.5  Nomenclature position.  of  the  vertical  planes  as s k e t c h e d  .. 100 mm  relative  / 48.7  through  i n F i g . 3.1. .. 1946  electrode  um.  the The  54  Smaller  values  results  due  for  r ••*• 1.285  the  mm  /  core  was  ym  Axial  (cannula  Distance This  center  z  0  between y  =  +1557, +3114  Insertion  as  was  d  deemed  cases  to  the f i b e r  deeper  than  o f 50  the  ym  fiber  yield  results  were  the  extrapolated  distance  diameter. or  unreliable  when  where  When t h e  the bevel was  r  the  center  was  not  » 18 mm  /  fiber).  along  /  0  0 ym  the  fiber  .. 2530  velocity  and the p o i n t  ym.  of 4  axis,  This  The  between  that  axial  corresponded  the dipole  center  (=  projects perpendicularly to distance  was  t o a time  varied  between  s p a n o f 632.5  ys  m/s.  y  of  between  the core,  four (core  as  distinct and  (fiber  t h e two h o r i z o n t a l p l a n e s t h r o u g h  shown  values  fiber  deeper  i n F i g . 3.1. y  =  -80  mm  /  The  vertical  -1557  i n same h o r i z o n t a l p l a n e ) ,  than  the  t  ym  (core  y  =  fiber  distance deeper  +80,  +160  was than mm'/  core).  Depth d distance  sketched  values  were  I n some  s e e F i g . 3.1.  the distance  the center  The  touching  touching  of the core;  was  ym  as the s m a l l e s t p o s s i b l e r e c o r d i n g  the distance  Distance  This  fiber),  was  48.7  then the smallest p o s s i b l e r e c o r d i n g distance  was  .. 130 mm  Vertical  varied  ym  /  gradient.  vertically  at a propagation  and  field  mm  i n t e r s e c t i o n o f a n AP)  the =  2.5  z  was  baseline  =  25  surface  facing the f i b e r , 350  r  to a high  leading-off of  than  =  d = 345  between  i n F i g . 3.2. 265, mm.  345,  425  the surface  of the s a l i n e  The i n s e r t i o n mm  /  5157,  d e p t h was  6714,  8271  t o the t i p of the  v a r i e d between t h r e e ym.  Standard  cannula, distinct  insertion  depth  55  Relative  Position  The parallel back  of  fiber. fibers".  CN  of Electrode  electrode  t o the f i b e r a  vertical  was  For reference, Figure  3.2  Fibers  always  axis.  plane  and  positioned  Thus  through  the  illustrates  the fibers the center  fibers  so  were  the  were of  divided  the beveled  either  the core into  o  "front  O  I  o  0  9  o o 9  9  O 9  Figure  3.2.  Front  and back  fibers;  insertion  depth.  fibers"  was  or at the  and p a r a l l e l  o  9  surface  i n front  situation.  9 o  that  and  to the "back  56  The  following abbreviations  case) of  the  AP's  were u s e d ;  and  conversion  cf. also Fig.  factors  ( f o r the  model and  real  1.5.  PTPA The which  peak-to-£eak  was  half  the  amplitude.  PTPA  for  The  ordinate  i n the  I  0.0305 A  ( s e c t i o n 2.6)  =  2.0226  x  10~  amplitude/PTPA. the  appropriate  a  p l o t s was  vm.  3  The Thus  value  values  symmetrical  measured  AP  as  and  o =  1.2  also  1/4ira  only  peak  by  dipole  contain  the  of  the a)  ( d e s i r e d I and  a  [dimension  mho/m ( s e c t i o n 2 . 2 ) .  multiplication  1/4 TT a  were  generated  calibrated in units  plots  the of  The  correction  m  - 1  source.  ],  This  gave  factor  2  amplitude  in  yield  true  the  amplitude  the  where I/4na  =  for  peak  results  with  PTPA.  PTPD The the  p_eak-to-peak d u r a t i o n  positive z-axis,  from  z  [mm]  1.2/  1.3).  to The  the  or  i . e . only  true  PTPD  conversion  rise  time.  h a l f the  [us]  The  true  measured v a l u e s  PTPD.  for a propagation  f a c t o r was  9.73  us  were  i n mm  in  A l l results  were  converted  velocity  4 m/s  (section  PTPD p e r  1 mm  of  distance  z.  SD The as  Key  spike  f o r the  duration.  PTPD a b o v e  The  results  i n d i c a t e the  true  SD.  The  same  remarks  data  points.  apply.  Symbols The  key  symbols are  used  on to  the  curves  The  symbols  identify  The  m e a s u r e m e n t s were made a t  the  conversion  f a c t o r s , see  the  do  not  curves  "even" v a l u e s  above.  necessarily represent at  "even"  f o r r and  abscissa values z i n the  model  [um,us].  [mm]  .  For  57  3.2  The  Wall  The  mechanisms o f  results were  for  Effect  the  presented  and  the  the  acrylic  The  and  where r  area  of  doubled.  the the  to  the  AP  not  the  doubled  the  60  a  wall  cm  (section  wall  due  by  3.6).  The  'Core'  Measurement tion the  2.5) signal  were  ym  that  a  for  I t was  a  mm  in section  elliptical "genuine  seen  29.8  (60  did  cm  that  /  150  ym  2.4.  x  Also  leading-off  insulator"  due  for  to  the  580  (plexiglas)  finite  ym  the  surface  the  size PTPA  needle,  alter  The  measurements small  finite  other  wall  shape in  elliptic  size  numerical  shown i n s e c t i o n  a an  leading-off  surface.  With  mm  to  100  the  &  the  mm  effect  48.7  ym  was  T r o n t e l j , 1979)  this  180  /  of was  Ekstedt  recorded  wall  for  1946 quite  the  shape  of  stated  s i g n a l but  merely  produced  results  this  (1964)  showed  late  SF)  (compared  i n v e s t i g a t i o n with 2  much  to  not  insulating wall  effect.  of  mm  amplitude  large  increase  wall  had of  insulating walls  amplitude  F i g . 2.10 diameter  Stalberg  the  the  times  peak, very  2.5, the  2.5  the  not  the  =  for this  by  2000  a l l r  after  in section  or  2  diameter  unaffected  smaller  No  the  described  even  concentric  and  from  2.6)  x  portions  those  to  15  doubled  remain  were e x p l a i n e d  ym.  /  AP  SF  from those a l r e a d y  3.3  ram  effect  exerted SD  mm  electrode'  amplitude. 2  7.7  < 50  implied  example  true  0.8  for  This  did  of  PTPA was  for  effect  (Fig.  insulating wall  However,  large  effect  arising  compared  'wall e f f e c t  electrode  that  effect  insulator  surrounding  ym.  wall  wall  "metallic insulator" (Pt).  doubled only  larger  the  that a  the  the  wall  shorter  than  portions were  both  of  the  extracted  AP  apart  2.4.  Alone results already  measured  of  the  presented  with  the  Au  plated  in  'core'  section  'core'  2.4,  electrode  electrode Fig. was  2.6.  (described It  was  distorted  by  in  sec-  seen  that  shunting,  58  "metallic  wall  attenuation decrease I/4TTO"]  at  r  for r vs.  encloses where  effect"  r  50  the  two  length As  due  field  a  graphs the  higher  according  that  no  possible. mV,  r =  trode in  The  2.5  3.4  computed  The  corresponding I t should  f o r the  AP  the  the  within  r.  [in units  to  &  &  r was  um  r =  noted  that  averaging with  pm  the  the  'core'  a  of to  (1973), in  this  steeper the  average pm  of  ellipse.  available  so  potentials  was  data  480  the  point  point  the  only  also  computed  were  at  according  i s not  much  the  obtained  48.7  pm  x 580  pm  were n o r m a l i s e d -1  500  simply  500  practically  =  10%  figure  Stalberg  2s  150  =  The  Stalberg  was  the  2s  t o PTPA 474.6 m ,  recorded  PTPA  Ekstedt  length  i n F i g . 3.3  potential  than  PTPA w i t h  points  be  less  opposed  potential  again  and of  PTPA  elec-  measurements  effect  that  is  electrode.  'Core & I n s u l a t i o n ' Assembly be  annular  epoxy  insulation  counteracted 2.4,  the  the  downplayed  the  insulation'. electrode At  (as  and  value,  Ekstedt  'core*  distortion  could  pm.  from  The  simulated  50%  alone.  redrawn  dipole  about  'core'  small  of  was  values  the  um  effect  absolute  decline of  the  results  It  tion  of  true  for  number for  the  and  100  the  1.1.  results  investigation,  responsible  =  gradient  large  i n F i g . 3.3.  this  2s  overall  shows t h e  graphs  result,  comparison  mm,  3.3  to  electrode  was  Eqn.  a  no  direct  a  to  p o t e n t i a l s of  Unfortunately,  Figure  corresponding  dipole  The  compared  point  investigation). to  averaging.  um,  >350 um. for  the  the  =  and  expected  annular, effect Figure  50  pm,  the  decrease  elliptical of  3.4 the  about  wall  surrounding  potential  l a y between  r —  that  the caused  due  demonstrates  50%  of  core by  insulating  shunting,  graphs  effect  of the  resulting was the  wall  a  core.  the  enhanced  that  the  PTPA  point  and  PTPA d e c r e a s e  As  was  surrounding  of  wall the  'core' was  the  elliptical,  compensatory  to  the  from  factor  noted  the  core  effect  'core  &  electrode  compensated.  of  that  in  sec-  further 'core  &  insulation' for r At  <  175  r =  175  59  50  F 1pure  3.3.  100 150 200 250 300 RECORDING DISTANCE R (MICROMETERS)  • 350  T h e PTPA v s r o f t h e p o i n t a n d t h e ' c o r e ' e l e c t r o d e for a d i p o l e l e n g t h o f 2s = 500 „m. A l s o shown a r e t h e c o r r e s p o n d i n g c u r v e s f o r 2s = 100 „m ( E k s t e d t & S t a l b e r g , 1 9 7 3 ) . G e n e r a t e d by a f r o n t SFP ( y = 0 ) .  400  60  Figure  3.4.  T h e PTPA v s r o f t h e ' c o r e & I n s u l a t i o n ' compared t h e p o i n t a n d ' c o r e ' e l e c t r o d e ; f r o n t SFP ( y = 0 ) .  to  61  ym,  t h e compensation  assembly  recorded  relative  PTPA  was  larger  vs. r  insulation'.  The  PTPA's t h a n  in %  at r  wall  effect  o f t h e 'core  true  PTPA. size  not  large  At  r =  dotted  arising  That  enough  t o exert  800 um t h e f a c t o r line  annular the f u l l  was  i n F i g . 3.5 i n t h e case  takes  place.  1.4  wall effect,  signals  insulation  and  &  completely  increase  due t o t h e  o f about  140% o f t h e  decreased  surrounding  steadily.  the core  was  f o r a l l recording distances r . t o 1.25 a t r =  graph  would  3.5 shows t h e  was  of  the  1800 ym.  PTPA  leading-off surface  graph  The Complete C o n c e n t r i c Needle core,  insulation  effect  small  The d o t t e d (full  wall  a maximum  insulation'  and t h e 'core  'core'  & insulation'  estimated  of a very  o f 200% a t s m a l l e r r  When  reached  epoxy  the  &  Figure  the amplitude  and decreased  i s an  r t h e 'core  f o r t h e 'core'  from  was w h e r e  & insulation'  of the e l l i p t i c a l ,  averaging  3.5  ym.  PTPA,  F o r r > 800 ym, t h e PTPA o f ' c o r e  insulation'  value  > 800  decrease  larger  the point electrode.  o f the true  PTPA  ineffective  The  100%, and f o r even  The  f o r 'core  &  w h e r e no p o t e n t i a l  eventually lead to the ordinate  factor 2).  Electrode  cannula  were  a l l  assembled,  three  different  c o u l d be p i c k e d up:  (i)  the core p o t e n t i a l  (ii)  the cannula  w . r . t . t h e remote  potential  w.r.t.  e l e c t r o d e , o r 'core  t h e remote  electrode,  or  v s . remote'; 'cannula  vs.  remote'; (iii)  the core tially,  In and  order  remote'.  o r 'core  w.r.t. the cannula  values  'core  errors,  a l l cases  v s . cannula'  d i f f e r e n c e o f the measured The m e a s u r e d  potential  as measured  differen-  v s . cannula'.  t o check- f o r m e a s u r e m e n t  t h e measured  obtained  potential  values  and t h e computed  ( i ) .. ( i i i ) w e r e  compared 'core  case  with  the  v s . remote'  ( i i i )d i f f e r e d  recorded  mathematically  and 'cannula v s . by  a t most  10%,  62  Figure  3.5.  T h e PTPA i n °/„ o f t h e t r u e PTPA v s r o f t h e 'core' a n d ' c o r e & i n s u l a t i o n ' e l e c t r o d e ; f r o n t SFP ( y = 0 ) .  63  indicating supplied tic  t h a t the  reliable  mean v a l u e  taken  as  the  The  results.  of  the  comparison the  individual  s i m u l a t e d MUP  measured  and  computed  of  the  effects  of  the  c o n f i g u r a t i o n of  ments y i e l d e d a whole.  cussed  3.6  to  i n section  of  improve  3.6  from  a  are  compared longer  any  'core  remote*  section  vs.  3.9)  cannula'  potential  & insulation'  insulation signal  with  the  apparatus  an  arithme-  potentials  the  "ideal"  was  signal  the  the  potentials  shed  light  cannula.  On  cannula'  point  causes  p r o p e r t i e s of  and  'core'  'core vs.  knowledge of t h e  the  and  and  p r o p e r t i e s and  the  other  (the r e g u l a r  electrode  distortions  of  onto  measure-  of  the  CNE  i t s shortcomings,  CNE. T h o s e  matters  new  are  dis-  Measurements  PTPA v s .  vs.  drawn  effects  the  not  of  The  for  similar  for a  potential  &  decrease  PTPA d r o p p e d b e l o w t h e  graphs  'core  minor  the  'core  measured of  comparison.  subtracted  case  r i n % of the  cannula'  fiber.  indicating  was to  front  very  obvious  potential  'core  also  cannula',  ever,  (see  electrical  3.10.  shows t h e  and  PTPA was  vs.  the  Amplitude  remote'  electrode  CNE) the  the  Single Fiber Potential  assembly  'core  epoxy  the  with  vs.  differential  evidence  sought  Figure  the  new  of the  Together  Peak-to-Peak  vs.  'core  sub-assemblies  recording  were  w e l l as  the  comparison  ways  model as  For  hand, the  as  tank  evaluation basis.  measured with the  electrolytic  &  insulation*. to  can  be  effect.  presence  the  true value present  the  complete  ' c o r e ' and  insulation*,  electrically,  due  with  the  It  cannula  cannula  t r u e PTPA, f o r t h e  seen  'core  For  r  effects i n the  that  When r  PTPA  electrode insulation' r  < 200  when t h e  um  at  core;  conductor.  how-  cannula reduced  (where t h e r e section  um  'core  larger,  drastically  > 1200  volume  &  for  became  Even  was  the  CN  'core  v s . remote' and  occurred. the  'core  cases  was  2.4)  This  no the  poten-  p o i n t v o  e l e c t r o d e  «  t r u e  P T P A  =  100%  ' c o r e ' ' c o r e  &  i n s u l a t i o n '  •  c o m p l e t e  CNE  ( ' c o r e  v s  •  c o m p l e t e  CNE  ( ' c o r e  v s  r e m o t e ' ) c a n n u l a ' )  400 600 800 1000 1200 1400 RECORDING DISTANCE R (MICROMETERS!  1600  1800  T h e PTPA 1n % o f t h e t r u e PTPA v s r o f t h e c o m p l e t e CNE ( ' c o r e v s r e m o t e ' , ' c o r e vs c a n n u l a ' ) , compared to the 'core' and ' c o r e & I n s u l a t i o n ' electrode; f r o n t SFP ( y = 0 ) .  65  potential  decrease  presence  signal  e v e n more When  of  the  remote', fiber true  true  The  cannula  the  core  A  signal  to a  fibers,  full  were  also  section  cannula.  mode/  distortion  b y t h e mere  the cannula  picked  v s . cannula'  electrode.  back  'core  fiber  which  SFP.  a  the  back  much  large portion  recorded  f o r values contained  remote'  =  115% 0)  signal  from  the e l l i p t i c ,  annular  massive  pronounced  'cannula from  vs.  a  back  t o 40%  of the  of the true  value.  'core  a back  b u t more  10%  was  PTPA  a  o f t h e PTPA i n  and  between  and  (at y  than  the  the signal  the cannula  of the cannula  only  of the e l l i p t i c  70%  differential  displays  that  only  fiber  smaller  a  configura-  bevel,  a r e t h e graphs vs.  was  between  For comparison, was  3.7  Shown 'core  v s . remote'  from  of the electrode  I t i s seen  produced  Therefore graph).  signals  up  ,  Figure  even  larger  than  vs. cannula' from  a front  fiber.  distant  Back  from  was fiber  fibers  the  core.  p a r t o f the cannula  but  core.  d i f f e r e n c e s i n t h e PTPA b e t w e e n  Peak-to-peak  graph  a  arising  which a r e i m p l i c i t l y  Figure  the  h o w e v e r , "saw"  aspect  Drastic  field  t h e PTPA o f t h e ' c o r e  f o r the  the  front  (dotted  close  Front the  by  also plotted,  were  to a  a t t h e back  o f t h e CN  from  signal1  negative was  up  was  by  value,  recorded  value.  lowered  fiber  exerted  property  picked  attributed  ( s e e a l s o s e c t i o n s 3.7, 3 . 9 ) .  was  directional  be  In the d i f f e r e n t i a l  which  the active  shielding  %  only  of the cannula.  considerable tion  could  of y  *  0.  i n t h e MUP  signals No  from  separate  curves  front  results  and back  fibers  a r e shown  here  (section 3.9).  Duration 3.8 p r e s e n t s  t h e PTPD v s . r f o r t h e v a r i o u s  i s t h e f u n c t i o n PTPD = r / 2 / ( 4 m / s ) , 3.1).  According  t o George  (1970),  including  electrodes.  a l l conversion  t h e asymptote  The  dotted  factors (see  of the locus  o f 9<f>^/3z  66  120  -i  ] io A 100  cr  10 A  • a * o •  CL  60  50  A  40  A  30  A  20  A  10  A  p o i n t e l e c t r o d e » t r u e PTPA » 100% ' c o r e vs r e m o t e ' , f r o n t ' c o r e vs r e m o t e ' , back ' c a n n u l a vs r e m o t e ' , f r o n t ' c a n n u l a vs r e m o t e ' , back ' c o r e vs c a n n u l a ' , f r o n t ' c o r e vs c a n n u l a ' , back ( n e g a t i v e ! )  i • • • i • • .• i •  200  Figure  i > ' • i • • i i • i •|  400 600 800 1000 ] 2 0 0 1400 RECORDING DISTANCE R(MICROMETERS)  3.7  1600  1800  The PTPA In % o f t h e t r u e PTPA v s r o f t h e c o m p l e t e CNE ( ' c o r e v s r e m o t e ' , ' c a n n u l a vs remote', 'core v s c a n n u l a ' ) ; f r o n t a n d b a c k SFP ( y = 0 ) .  Figure  3,8.  The PTPD vs r of the point, 'core', 'core & Insulation' e l e c t r o d e and the c o m p l e t e CNE ('core vs remote', 'cannula vs remote', 'core vs c a n n u l a ' ) , compared to the asymptote of the locus for the theoretical PTPD (according to George, 1 9 7 0 ) ; f r o n t SFP ( y = 0 ) .  O "  J  68  = 0 ( d i f f e r e n t i a t e d Eqn. 1.1) i s given by z = r//2. should coincide with the asymptote.  Where z »  s, the PTPD  Due to the p o t e n t i a l d i s t r i b u t i o n devia-  tions i n the tank f o r large r ( c f . section 2.3) the measured curve never quite reached the asymptote.  For points z + s close to the dipole, the PTPD equals  2s/(propagation v e l o c i t y ) .  This was found to be true f o r the point, 'core' and  'core & insulation" electrodes which a l l shared the same curve as seen i n F i g . 3.8.  The shortest PTPD of 125 us f o r r + 25 ym was d i r e c t l y dependent on the  dipole  length 2s = 500 ym.  Since the PTPD vs.  r was the same f o r point,  'core' and 'core & insulation* electrode, i t was concluded that neither shunting nor wall e f f e c t nor averaging trast,  the presence  influenced the PTPD measurably.  In con-  of the cannula produced a shorter PTPD of the 'core vs.  remote' s i g n a l f o r r > 200 ym.  A slope of 7 2 / 4 was also established f o r r >  1200  ym with a constant difference of about -60 ys. The PTPD of the 'cannula  vs.  remote' signal was very long.  I t was on average about 200 ys longer than  when p i c k e d up with the p o i n t e l e c t r o d e . maintained  An approximate slope of / i / 4 was  for a l l r . The long PTPD of the cannula signal was responsible f o r  the short PTPD's measured d i f f e r e n t i a l l y /2/4 was reached  'core vs.  cannula'.  The slope of  f o r r > 1600 ym with a constant difference of about -180 ys  compared to the true value. Figure 3.9 i l l u s t r a t e s the d i f f e r i n g PTPD's f o r front and back SFP's. The highly asymmetrical  beveled t i p of the electrode influenced the shape of the  recorded SFP's s i g n i f i c a n t l y .  I t can be seen that a back f i b e r produced a very  much longer PTPD recorded with the 'core vs. remote' and a shorter PTPD recorded with the 'cannula vs. remote', both compared to a front f i b e r .  The r e s u l t  was a shorter PTPD recorded d i f f e r e n t i a l l y 'core vs. cannula' from a back f i b e r than when picked up from a front f i b e r .  PTPD's f o r values of y * 0 are i m p l i -  c i t l y contained i n the results of MUP's (section 3.9).  A  Figure  6  3.9.  T h e PTPD v s r o f t h e c o m p l e t e CNE ( ' c o r e ' c a n n u l a vs remote', ' c o r e vs c a n n u l a ' ) b a c k SFP ( y = 0 ) .  vs r e m o t e ' , ; f r o n t and  70  Spike  Duration The  Pig.  3.10  3.8. was  SD  was  somewhat  e x h i b i t e d t h e same  The  SD  of the signals  essentially  shorter along  SD  t h e same  where  r  slightly  100  ys f o r r  for  small  •*• 25  (Figs.  cannula'  due  electrically shorter  ym.  not  than  Figure  to  true 3.11  3.5, a  very  It  compares  the  shown  insertion  volume surface  very  area  expression  is  due  & insulation'  to a  value.  SD  'core*  electrode  recorded  wall  a 50  effect  r , t h e SD  due  t o t h e PTPA  the  'core  SD  tended  physically  obtained  vs.  present  with  remote' cannula  30%  'core v s . 'core  vs.  signal.  alone  The  caused  t h e SD's a r i s i n g t o t h e PTPD  from  and back  ( F i g . 3.9).  f u r t h e r accentuated f o r values  front  Both,  fibers.  a  the shortened  the directional  o f y * 0 from  front  Again,  property  and back  by  Cannula  Pollak into  along  fibers are  I n s e r t i o n Depths  (1971)  that  the tissue.  the  exposed  * V(r ) • O  SD  of the  surface to  the  potential  of  the cannula The  average  the cannula  tissue.  Pollak  potential of  decreased  A  ;  becomes  smaller  developed  the  when  r  O  more  following  V  where X »  with  the p o t e n t i a l s i n the  r C  than  i n t h e MUP's; c f . s e c t i o n 3.9.  f o r the cannula  V  to  o f about  v s . remote' and  was  'core  decrease  us  factor  The d i f f e r e n c e s were s m a l l e r  shortest of  varying  For small  & insulation',  but  o f t h e SD  depth  conductor  was  mainly  The  similar  of Different  was  'core  and t h e  SD.  contained  Effect  was  connected  t h e PTPD o f b a c k f i b e r s  3.7  This  long  and  implicitly  The  f o r t h e SD v s . r i n  f o r t h e PTPD v s . r i n F i g .  the point  i n s e c t i o n 3.2.  3.6).  tendency  The r e s u l t s  with  'core  the  CNE.  was  recorded  the true  This  r , i n a l l cases  cannula'  as t h e graphs  ym.  than  The graphs  tendency  mentioned  longer  t o t h e PTPD.  for a l l r.  > 500  z, as a l r e a d y  become  related  (3.1)  71  1400 -, 1300 1200 1100 rr if) a o c_>  1000  UJ C/)  900  4  5  800  4  o or  a  700 600 4 500 4 400  • point electrode o 'core' o 'core & i n s u l a t i o n ' •complete CNE ( ' c o r e vs remote') A complete CNE ('cannula vs remote') •complete C N E ('core vs cannula')  300 200  '  I '  r  ~  100  Figure  3.10,  1  '  I  1  —'—'—  1  | ' — i — ' — i — j — r — i — i — i — | — i — i — i — i — | — i — i  ,  i—|—r-  200 300 400 500 600 700 RECORDING D I S T A N C E R (MICROMETERS]  T h e SD v s r o f the point, 'core', 'core & Insulation' e l e c t r o d e a n d t h e c o m p l e t e CNE ( ' c o r e v s remote', ' c a n n u l a vs r e m o t e ' , 'core vs cannula'); f r o n t SFP ( y = 0 ) .  800  72  a  a  RECORDING  F igure  3.11.  DISTANCE  R  (MICROMETERS)  The SD v s r o f t h e c o m p l e t e CNE ( ' c o r e ' c a n n u l a vs r e m o t e ' , ' c o r e vs c a n n u l a ' ) b a c k SFP ( y = 0 ) .  vs r e m o t e ' , ; f r o n t and  73  X i s the length of the cannula i n contact with the tissue (corresponding to d) and r  Q  the r e c o r d i n g d i s t a n c e r as d e f i n e d i n section 3.1.  only v a l i d  i f the s p e c i f i c  interface impedance between cannula and tissue i s  much larger than the bulk r e s i s t i v i t y of the e l e c t r o l y t e volume  conductor  Equation 3.1 i s  currents; see  section  2.4).  In  (no shunting of the  addition,  Eqn.  3.1  was  developed f o r a front SFP at y = 0. Figure 3.12 presents the graphs of the cannula PTPA vs. r for three i n s e r t i o n depths  d = 265  .. 425 mm  / 5157  .. 8217  um.  cannula p o t e n t i a l resulted for deeper i n s e r t i o n . 3.1  were a l s o drawn f o r comparison*.  As expected, a decreased  The graphs according to Eqn.  Pollak*s estimate of V  c  was  reasonably  good where r > 20 mm / 38.9 um. For r < 20 mm, however, Eqn. 3.1 underestimated V . I t should be noted that not only the r a t i o of cannula and core PTPA c J  alone was  an important aspect for the d i s t o r t i o n of the d i f f e r e n t i a l  but also the PTPD and SD of the cannula p o t e n t i a l .  signal,  Equation 3.1 did not supply  the l a t t e r information and could therefore only be used as a rough estimate of the cannula p o t e n t i a l and i t s dependence on the i n s e r t i o n depth f o r a SFP. Figure  3.13  shows the r e s u l t s of the cannula  i n s e r t i o n depths, where y = ±80 mm (cf. sections 2.2,  3.1)  i t was  depths d for both values of y.  / ±1557 um.  PTPA vs. r f o r d i f f e r e n t  Due to mechanical  limitations  not possible to take the same two  insertion  However, the difference of i n s e r t i o n depth  i d e n t i c a l i n both cases, namely Ad = 80 ram / 1557  ym.  was  I t i s evident that when  y * 0 the cannula p o t e n t i a l underwent smaller changes f o r varying i n s e r t i o n depths than when y = 0.  I t can also be seen that f o r r < 600  ym the absolute  For V ( r ) the PTPA's recorded with the point electrode were taken ( F i g . 3.3). Q  74  F1qure  3.12.  The cannula PTPA v s r for different Insertion depths d. Also shown are the curves of Eqn. 3.1 (Pollak, 1 9 7 1 ) ; f r o n t SFP ( y = 0 ) .  500  -i  I -• • • i • • • i • • • i  0  200  F1qure  3,13.  i .. i | i  400 600 800 1000 1200 1400 RECORDING DISTANCE R (MICROMETERS)  The cannula PTPA v s r for d e p t h s d ; f r o n t SFP ( y * 0 ) .  different  ,  1600  1800  insertion  76  cannula than  PTPA  was  the  case  in  larger y  cannula p o t e n t i a l Figure where t h e  3.14  of  < 100  the  the  insertion  25%  (d =  8271  for  larger  ym)  depths  ym  and  was  tial  be  45%  (d =  half  front  3.1  d i d not was  SFP  at y  always  at  applied section  =  100% on  5157  the  1%  at r =  least  In a  potential. cannula  that  60%  for y  =  +1557  that  of  The 1600  the  rough  reality,  whole  MU.  recording.  ym.  estimate  however, The The  of  formula  case  the  could  fibers  the  y =  0 and  at  y  # 5%  insertion of  reached  the  cannula  cannula  -1557  the  fiber  depth.  cannula  i n Eqn.  cannula p o t e n t i a l s  3.1  itself.  active  i s inadequate  o f a MU  It  poten-  potential  f i b e r i s never  The  =  cannula p o t e n t i a l  the  that  t o 10%.  of  r  differing  for y  location  the  0,  a  f o r the  entail a  more t h a n  than  PTPA, a s  demonstrates  core p o t e n t i a l  a single  um  of  potential  This  relative contribution than  -1557  aspects  remote'  cannula  Thus the  cannula p o t e n t i a l  i s more i m p o r t a n t a  ym.  =  c o r e PTPA e v e n  depth  the  y  i n a r e l a t i v e manner  i n the  the  potential  and  the  'core v s .  For  at  MU's.  of  ym).  40%  the  supplies  0.  core  between  over  t o motor u n i t 3.9.  treats  +1557 um  I t i s seen  ym)  a l t e r the  emphasized  only  - 1 5 5 7 , 0,  exceeded  (d =  5157  the  t o the core p o t e n t i a l  Equation  3.9  distances a smaller insertion  almost  to well  also  smaller for a l l r  i n % of  r.  never  tested  of greater influence  should  but  potential  to  potential 80%  and  Section  i s plotted  distance  depth  recording  insertion  um  compares a l l c a s e s y =  cannula  of  +1557  ( F i g . 3.12).  recording  potential  =  i n more d e t a i l i n c o n n e c t i o n w i t h  smallest  cannula  0  cannula p o t e n t i a l  function um  =  at y  for  a  alone when  are t r e a t e d  in  77  RECORDING DISTANCE  F Igure  3.14.  The c a n n u l a for various  potential v a l u e s of  R(MICROMETERS)  in % of the c o r e PTPA d and y ; f r o n t S F P .  vs  r  78  . 3.8  tial  The  Motor U n i t  The  SFP  Model  discussed  averaging,  so  f a r made i t p o s s i b l e  insulating wall,  d.  Yet  practically,  for  r e a s o n s w h i c h were e x p l a i n e d Many  Buchthal the 5  of  that  et  mm.  least  al.  muscle  200  lies  over  The  the  radius  =  700  uptake  defined  9.5  to  5%  tion;  cf. Under  the  the  section the  have  ground'  of  array  value  recorded  of  of  an  163  y  and  for single fiber  EMG  structure  a  MU.  unit  in  &  of  circular  /  (1980)  of  obtained to  Lambert,  fibers  one  with  number  reported  mm  (1.35  =  2  8.3  fibers  /  300  mm ).  The  uptake  or  as  the  recording fiber  (r  «  25  MU  of  at  um 5  /  mm  radius  where t h e  pra i n t h i s  2  uptake  fibers  pickup r  et a l . ,  fibers  /  distance  one  randomly  Stalberg  (average  the  in  estimate  (1975)  2  diameter  uniformly  1973;  19.6  fibers an  be  of  a mean  Boehle  at  of  motor  &  extensive  amplitude  been tank  and  difficult  that  was  front  shape o f  surface  model.  five  homogenous  a l l i n d i v i d u a l SFP's  leading-off  fibers with  fibers  territory  average  was  Thiele  T r o n t e l j , 1979)  The  the  electrolytic  arrangement  6.5  the  ( i n press)  Stalberg  and  2  =  by  of  values  poten-  / is  PTPA  investiga-  3.1).  1853).  would  mm )  assumption  l o c a t i o n of It  the  of  &  density  on  nearly  (Brandstater  observed /  & Gath  e f f e c t s of  varying  never used  the  the  arrangement  territory  superposition  Principle,  fiber  radius  (Stalberg  drops  Stalberg  the  1.6.  that  estimated  assess  fibers,  information  b r a c h i i m u s c l e was  The  fibers  in section  reported  (1959)  range  back  i s almost  furnished  1973)  163.  the  electrode  resulting fiber  within  um  as  fibers.  scattered  the  (1957,  Christensen  1976).  CN  investigations  n o r m a l human b i c e p s  of  is  the  f r o n t and  to  and  the  3.15  to  back  model  fibers  MUP  the  represent  Figure chosen  belonging  within  to  volume to  the  i s very  MU  the  MUP  (Helmholtz'  much d e p e n d e n t  on  MU.  a  random  depicts a  conductor,  MU.  each  at  scatter  the  of  fibers  simplified  It consisted  of  r  60,  =  20,  40,  in  spatial a  'back80,  100  79  o  o  o u  o  o  o  o  o  o  o  o  o  o  o  o  o  o  • 160 mm  o  o  o  ij ' £0 mm  frma  back  'backijnmi'  o  o  o  <j-0  t o  F jgure  mm  •o  3,15.  o  o  -80  (just  fibers.  In  pseudo-random 2.5 mm  composed the  below order  SO n o  o  o  I  o  o  o  o  levels  simulate  tip). four  Thus  y = 1 6 0 , 80 0, -80 mm was a s s u m e d  different  MUP's  / 48.7 o r 5 mm  / 97.3 um o r 10 mm  o f t h e 41 f i x e d  'background' f i b e r s (recording distances  /  fiber  195  plus  um.  was p l a c e d three  t h e one f i b e r  as above).  contained  (corresponding  Thus  /  a t r = 0, y =  t h e 'background' a r r a y  e l e c t r o d e p o s i t i o n s ) one a d d i t i o n a l  leading-off surface  o  Another 'background' f i b e r  the cannula to  o  T h e m o t o r u n i t model f i b e r a r r a n g e m e n t w i t h 41 'background' f i b e r s and 1 nearest fiber a t r = 2 . 5 , 5 . 10 o r 20 mm / 48.7. 97.3, 195 o r 389 j,m.  1 5 5 7 , 0, -1557 um.  mm  o  J n*ar«t fibers  / 3 8 9 , 7 7 8 , 1 1 6 8 , 1 5 5 7 , 1946 um a t t h e f o u r  3114,  =  o  o  • <  'background'  to  41  four  a t y = 0, r MUP's  very  were  close to  T h e f o u r t h MUP  simply  80  consisted mm  /  the  389  of  the  um).  41  That  tendencies  fibers  do  distant fore the  model  ferent  MU  of  2.9  1979)  of  fibers  (i)  FD's  effects  estimated fibers 0.7  mm.  fore  This  the  were  a  5)  that  represented  only  /  mm  of  assess distant  the  very  There-  in  a  MUP  fixed  volume  the  much.  arrangement. conductor Thus  clinical  EMG  while  Only  four  CN  dif-  electrode  closest the  the  influence  the  the  fibers  distances  a  seven  MU  fiber  FD.  density  nearest  The  FD  (within Thiele  contributing  FD  20  to  when a l l 41  2  the  full low  to  more  =  of  variable.  in  r  arrangement  only  recording  conductor,  at  varying  a  made  where  so  fibers  yielded  model  in  to  more  to  the &  FD  between  2  to  3  fibers  uptake  MUP  2.6 /  MU  the  distant  mm  2  were e n c l o s e d ,  in  the  vicinity  (1975)  15.6  kept  & or of  lower  reasons:  area)  within  and  Stalberg  m o d e l was  three  Boehle  the  a  fibers  for  ('FD*;  fibers  i n the  preceding paragraphs)  the  with  kept  which  were c o n s i d e r e d .  of  (mean  was  was  deemed s u i t a b l e  volume  contribution  fiber  position.  3.15  (see  was  A  case  their  2.2  the  array  the  a  closest  MUP.  muscle  when  2  surface  reported The  mm  of  MUP,  relative Fig.  In  fibers,  the  the  about /  spike  fiber  changed  in  ( i . e . the  representation  their  modeled  their  model  leading-off the  the  affect  in  surface  MU  to  PTPD o f  slightly  preserved  Trontelj,  than  and  MU  closest  arrangements  leading-off  The  the  fibers  behaviour.  'background'  PTPA  moved  of  CNE  does not  the  the  the  fibers  mainly  about  of  contribute  distances  fibers  solution  not  the  were  'background'  would  reported  an  uptake  fibers  represented  be  under2  to  12  radius  of  / mm . 2  a  "worst  Therecase"  situation. (ii)  (iii)  The  low  FD  MU  effects  of  front  To  minimize  arrangement  the  fibers  in  and  number o f  Fig. back  3.15  made i t e a s i e r  fibers.  computations  required.  to  separate  the  81  MUP's results, 48.7 the  is  only  t o 389 case  simply  were  obtained  the s u p e r p o s i t i o n of the data  the recording distance  ym)  i s indicated.  o f one f i b e r  refers  from  r of the nearest  So, f o r example,  a t r = 10 mm  plus  t o t h e 'background'  41  array  the recording distance of the nearest  Standard  insertion  depth  ym w h e r e  d = 425 mm  was d = 345 mm  fibers  r = 10 mm  'background'  alone. fiber  points.  ( 2 . 5 t o 20 mm  / 195  fibers,  ym  / 8271 ym due t o m e c h a n i c a l  r = 20  with  SFP's,  t h e 'background'  / 6714 ym, e x c e p t  mm r  array.  f o r y = 160 mm  limitations  /  represents  while  F o r comparisons without  In the  / 3114  ( c f . s e c t i o n s 2.2,  3.1).  3.9  Motor U n i t P o t e n t i a l  Cannula  Potential  Figure tion  ferences.  tial the  At  (dotted  arising core  r as parameter. the value "peak"  from  PTPA.  percentages late  3.16 d i s p l a y s t h e r a t i o  o f z, w i t h  signal  Measurements  of  line;  a S F was The  compared  z  the cannula  (all  r).  fact  t h a t many  3.14  i n section  cannula  potential  were  / core  potential  o f S F P a n d MUP  t h e peak  0.5% t o 4.3%  amplitude  to half  occurred  from  a  potential  func-  on  the  t h e PTPD) t h e c a n n u l a  ( r = 2.5 t o 20 mm  values  as a  reveal striking  MUP  a t z = 500  difcore  poten-  / 48.7 t o 389 ym) o f  were  10% t o 6 6 % .  t o t h e 2 5 % t o 30% r e p o r t e d b y B u c h t h a l  picked  The l a r g e c a n n u l a fibers  where  corresponding  portions of the recorded  section,  The p l o t s  corresponding well  i n % o f cannula  ys from  These  (1954).  the baseline  For inter-  u p 52% t o 57% o f t h e S F P a n d 84% t o 8 7 % o f t h e MUP potential  arising  from  c l o s e t o the cannula  3.7 i l l u s t r a t e d t h a t was l a r g e r  t h e MU was e x p l i c a b l e  b u t f a r from  t h a t a S F a t y = +80 mm than  the core  potential  the core.  / +1557  by t h e Figure  ym p r o d u c e d  when r < 800  ym.  a  82  1 0 0  N  Q_  I AXIS  Fjgure  3.16.  (MICROSECONDS)  The c a n n u l a p o t e n t i a l In % o f t h e c o r e p o t e n t i a l vs z f o r v a r i o u s v a l u e s o f r ; f r o n t SFP (y=0) a n d MUP.  83  Peak-to-Peak The  Amplitude  PTPA r e c o r d e d  MO  was  expected  as  F i g . 3.17  to  signal  the  This  SFP.  practically that  the  not  was  reported  400  as  a  CNE  measured  in MU  electrode  which  had  a  investigation area.  values  ferencs The  fiber, 389 core  reason same  as  the  was  with  ones  easily  The  the  PTPD  within PTPD o f  for  MUP  be  represented.  ym.  the  of  This  um  ym  to  to  to  450  pickup  Thiele &  also  um  the  radius  one  of  indicates value  was  (dotted  graph,  Thiele &  Boehle  smaller  value  fiber  the  DISA  compared an  dif-  remained  smaller  used  as  have  which  um  The  the  the  The  and  Boehle  um  than  um.  (1980)  attributed  only  340  the  confirmed  cannula'  •*• 25  r  mm.  &  vs. 400  1  could  observed  'core  from  was  potential  about  Thiele  diameter  650  of  Stalberg  700  That  smaller  cannula  50  remote'  that at r =  became  was  r =  of  could  S t a l b e r g and  with  already  the  SFP  the  CN  to  influence  lay within  40%  to  of  den13K53  the  CNE  on  the  60%  of  Boehle.  of r  determines  the < 20  the of  cannula mm;  MUP the  e l e c t r o d e d i d not  presented  understandable  which e s s e n t i a l l y  signal  radius  see  graph  from  vs.  for a l l r.  to  electrode  PTPA  cannula  PTPD's r e c o r d e d  ym.  CN  MUP  'cannula  Duration  from  fact  The  model  was  SF,  the  i n s e c t i o n 3.1).  Nevertheless,  Peak-to-Peak The  the  the  r e p o r t e d by  of  and  greatly increased  pickup  the  the  of  remark  which  pickup  a  the  interesting  for a l l r.  with  under  to  radius  see  (1975)  sity  due  remote'  from  cannula'  e x t r a p o l a t i n g the  measured;  ym  vs.  vs.  than  I t i s most  constant  by  'core  larger  'core  uptake  obtained  be  shows.  ferential  with  i n s e c t i o n 3.6  since the  the  was  c f . s e c t i o n 3.6  differential nearest  signal  fiber  i n the  noteworthy d i f case  recording distance  PTPD, was  signal  exhibit  at and  the  the  closest 20  larger  than  r =  least  double  the  PTPD  Figs.  3.8  vs.  array  and  3.9.  cannula'  even  SFP.  of  never  'core  i n the  of  though  of  For  remained the  mm  / the  that the  cannula  84  500 -i  400  A v • o * a • o  300  A  200  A  100  A  MUP SFP MUP SFP MUP SFP MUP SFP  /  point  }  ' c o r e vs remote"  1 J \ J  electrode  cannula vs remote . core vs cannula'  CL  '  I  1  — " — — r — | — i — r — • — i — | — i — i — i — i — | — i — i — i — i — j — i — r — t — i — ( — i — r  50  1  100  150  RECORDING  Figure  3.17.  200 DISTANCE R  250  300  350  400  (MICROMETERS)  T h e PTPA v s r of the p o i n t e l e c t r o d e and complete CNE ('core vs r e m o t e ' , 'cannula vs remote', 'core vs cannula') ; f r o n t S F P (y=0) a n d MUP.  85  potential PTPD's  was  for small  dictory  with  PTPD o f  112  for  tion  to  of  of  in  the  PTPA  ( F i g . 3.23).  i n both  SFP  literature.  for this  s h o r t e s t PTPD o f  4  vs.  and  MUP  (r =  25  of  was  unchanged  not  contra-  (1964) m e a s u r e d  (1955) o b t a i n e d  ys  fact  cases  Ekstedt  investigation  125  The  a mean PTPD o f  was  chosen  ym)  a  at  an  2s  =  121  ys  ym  in  500  assumed  mean  propaga-  m/s.  the  cated  rapidly  compared of r  SD  to both  point  3.6,  e x p l a i n e d by signal SD  was  true  and  the  MUP  the  SD  of  the  vs. r  the  for r  > 20  ym,  for  smaller than  from  the  to  mm  in  and  the  /  observed r  <  170  than  the SFP  The  very  flat  because PTPA  i t was  vs.  r  as  curve  PTPD  SD  was  on  shorter  or  also  50 r  ys =  short-  graphs  ym. indi-  signal,  interest. were  recorded  The  longer  with  the  already presented  SD  long which  true of  the  (over was  SD  SD  true  300  cannula'  signals  than  The so  at  i s of  MUP  longer  t r u e PTPA f o r s m a l l r .  ys  vs.  true SD  only  made, t h e  i n F i g . 3.18  f o r the ym.  was  'core  cannula'  long  remote'  350  were  the  vs.  respectively,  vs.  to  a  massively  signal  ym  of  aspect  the  'core  389  SD  'core  with  illustrates  differential  Another  same was  3.10,  signal  d i f f e r e n c e expanded  remote*  < 120  MUP  3.18  compared  i n c l u d e d i n F i g . 3.18  resulted 3.17.  Figure  value.  The  Fig.  not  ym  cannula  increasing deficit  electrode.  section  large  MUP.  signal,  'core ym  the  evaluations  the  < 180  50  core  no  a  of  cannula'  at r =  Although  Fig.  a  recorded  'core  than  long  found  impact  the  While  for  core  dipole length  of  main  the  SD's  the  Duration  SD  SD. er  The  produce  The the  of  recording distances  reports  velocity  Spike  60%  ys f o r SFP's whereas B u c h t h a l  MUP's.  order  over  could  cannula 2 ms).  in be MUP  This  presented  in  1 0 0 0  -,  RECORDING D I S T A N C E R  Figure  3.18.  T h e SD v s r o f t h e ( ' c o r e vs remote', (y=0) a n d MUP.  point 'core  (MICROMETERS)  e l e c t r o d e a n d c o m p l e t e CNE vs c a n n u l a ' ) ; front SFP  CO  a*  87  3.10  Special The  a  Electrode  results presented  considerable  source.  The  The  chief  the  signals  it  was  One  so  far  demonstrated  d i s t o r t i o n of  the  signals  main  picked  up  to  possibility  were by  to  as  SF  surface  i s usually  tal  end  the  a p p r o a c h was pose, 4184  the um.  (i)  try  distal This In  order  cannula  to  average The  tial,  was be  low  'KRYLON' E n a m e l  in  the  the  epoxy  within  from the  MU  human b i c e p s of  5 mm,  bare  part  muscle  impedance,  Spray P a i n t ,  see of  tissue  external  two the  over  undesirable  by  a  as  well or  simple  diameter  means.  length  the  The  For  are  leading-  to  exists.  as not  electrodes  close  MU  behaviour.  disother  that  of  215  had  p o t e n t i a l s , most to  b r a c h i i muscle section  to  r  or  whether  potentials.  2  SF  purmm  /  factors:  territory  the  um  SFEMG  cannula  insulated  to  sideport  about  the  vs.  Such  25  introduces  surface  CNE  surface.  resin in a  was  SD  as  the  circular,  literature  cannula  arose of  CNE  either  leading-off  fidelity  the  the  r and  question  "harmful"  shielded  diameter  to  where  that  from  PTPA v s .  leading-off  d e t e r m i n e d by  i n the  remaining  exposed  the  portion  territory  (ii)  of  length  the  Extensive reduce  The  recording  embedded  to  end  the  up  elliptical  cannula.  reduce  needle.  to  large  electrodes,  off  of  the  improve  was  known  the  clearly  picked  d i s t o r t i o n s were a f l a t t e r  "offenders"  possible  generally  Design  noise  Borden Products  was  insulated. reported  to  the  The  MU  have  an  3.8.  cannula act  be  of  as  must a  good  still  reference  rejection).  Ltd.,  be  Canada.  sufficiently (low  poten-  88  Figure  3.20.  The t y p e I I i m p r o v e d CNE ( i n s u l a t e d c a n n u l a t i p with bare annular, e l l i p t i c p o r t i o n ) .  89  The  insulated  construction insulation simpler The of  around  cannula  was  That  sharp  3.21  nula  t i p (type  This  was  cannula  a  f o r the regular, I ) CNE  the  dull  point,  A  cannula  without  the exception  i s flush  with  the  of the electrode bevel  altering  results  somewhat  i n F i g . 3.20.  but with that  The  because the  second,  I t i s shown  the grinding  and p r o m i s i n g  were  the  effect  of  obtained with  I I , as d i s c u s s e d i n t h e next  the  t h e new  paragraphs.  an  with  ideal  large  partially  leading-off  insulated  the r a t i o  was  of  factor  and  f o r r = 2.5 mm/ reduced  24%  portions  t o 1 0 % a t z = 625  cannula  t o 8%  potential  at z =  650  48.7  ys.  identical The  of  the  ys.  (directional  a t t h e same v a l u e o f z . was  signal  means  to f i e l d  ym a n d z = 140  ys.  that  the  SFP  were  I t was  con-  a type  I  distortions properties).  F o r r = 10 mm  F o r z > 250  cannula  was  a maximum o f 24%  f o r a l l r = 2.5  "peaking"  can-  f o r z < 150 y s .  t o 3.28) p i c k e d up w i t h  b u t r a t h e r due  the  which  poten-  insulated  differential  signal  Later  ( s e e F i g . 3.22 potential  potential  ( i ) . The  remote'  o f up  completely  cannula  electrode.  surface  The  ( t y p e I I ) CNE p i c k e d up o n i t s c a n n u l a  of the cannula  a value  small  vs.  a ratio  t o the cannula  the core p o t e n t i a l  percentage  with  t h e SFP d i s t o r t i o n s  n o t due  the  'core  reference  that  were  the  (SFP) i n % o f t h e c o r e  I a n d I I CNE.  according to design  identical  was  type  potential  had a n e g l i g i b l y  cluded  reached  of  compares t h e c a n n u l a  up b y t h e c a n n u l a  ym  off easily.  therefore realized.  part  with type  picked  195  wear  in reality  t h e same l e n g t h o f 215 mm  interesting  expected,  therefore  of  problematic  i n F i g . 3.19.  Potential  vs. z  The  over  to prevent  especially  tial  from  t i p might  I I ' , was  elliptic  Very  Figure  CNE  I*, i s pictured  d e s i g n would a l l o w i n p r a c t i c e  insulation.  Cannula  the  e l e c t r o d e , 'type  e l e c t r o d e c o u l d be  insulated  recommended  designs,  an  'type  annular,  bevel. as  o f such  design,  the  cannula  ys t h e  t o 10 mm  potential  /  and  curve  90  100  -i  9Q  -  80  ' c o r e v s remote" • • • * o  -  PTPA  = 100%  type I , a l l r type I I , r = 48.7 „m type I I , r = 97.3 nm t y p e I I , r = 195 „m r e g u l a r CNE, a v e r a g e f o r a l l r < 400 „m  70 A  0  Figure  /  100  3.21.  200 Z AXIS  300 400 500 (MICROSECONDS!  The c a n n u l a p o t e n t i a l 1n % o f z of the regular, type I v a r i o u s r; f r o n t SFP ( y = 0 ) .  600  700  the core p o t e n t i a l vs a n d t y p e II C N E . f o r  91  around  z =  annular,  140  us  elliptic  (this  i s not a t t h e peak  cannula  portion  the  r e g u l a r bare  see  F i g . 3.16, s e c t i o n 3 . 9 ) . Figure  MUP's.  z  =  and  shows  see a l s o  50  cannula 20 mm  3.22  ( d o t t e d graph,  the  us  after  potential  /  48.7  remarks  same  t o 389  as  of the type  I I new  'PTPA'  intersection,  3.5%  while  of a l l r ;  due t o t h e  and  600  figure  design 'SD'  but  i n this of  potential  us t h e p e r c e n t a g e s  bare than  curves  f o r the  ( t h e y were n o t  the percentage  t o 21.5% o f t h e c o r e  at z =  f o r the exact  the preceding  i n the paragraphs  from  um)  average  graphs  the baseline  ranged  was  w h i c h p i c k e d up a n e v e n h i g h e r p o t e n t i a l  N o t i n c l u d e d were t h e r e s u l t s  computed; At  cannula  of the core!)  section).  the type (r =  I  2.5 t o  w e r e b e t w e e n 52%  56%. Figure  Plotted  3.23 p r e s e n t s  were  t h e graphs  (corresponding type  I MU  a somewhat  of the cannula  potential  at r =  reduced  10%  t o 3.5%  For  comparison,  the corresponding  are  also  f o r t h e SFP.  given  than  5% o f t h e c o r e  tial  was e v e n  The regular face.  / 48.7  um a n d f r o m graphs  of the cannula  i n F i g . 3.21  (inversed  and  the r e g u l a r bare  PTPA  389  had um.  type  cannula  The  cannula  from  / 389  um.  I and I I cannula  potentials  The t y p e  vs. r  3.22).  66% t o 24% a t r = 20 mm  types /  potential.  i n % of the core  of the regular,  A l l three  negative  lines w.r.t.  PTPA w h e r e r < 20 mm  slightly  smaller  I cannula  poten-  phases).  Amplitude  type CNE,  2.5 mm  was  aspect  potential  t o t h e "peak o f t h e c o r e "  cannula  Peak-to-peak  different  I had due  Therefore  shown) b u t o n l y  a  larger  "insulating  t o the insulated, t h e SF PTPA  f o r r > 2.5 mm  annular  'core v s . / 48.7  wall"  um.  surrounding  cannula  remote'  was  The t y p e  portion slightly  the core  than  i n the bevel larger  I I b e v e l was  the sur-  (curve not  identical  with  92  Figure  3.22.  The c a n n u l a p o t e n t i a l i n % of the c o r e z o f t h e r e g u l a r a n d t y p e I C N E : MUP.  potential  vs  / 60 A • • v o •  50 A  MUP, MUP, SFP, SFP, SFP,  type I regular type I regular type II  40 A  30 A  20 A  100 200 RECORDING DISTANCE R  F igure  3.23,  300 (MICROMETERS)  The c a n n u l a p o t e n t i a l In % o f t h e the regular, type I and type (y=0) a n d MUP.  c o r e PTPA v s r o f II C N E : f r o n t SFP  400  94  the  regular bevel.  I I was  identical  Figure and  recorded due  real  the  PTPA  r e g u l a r CNE SF  PTPA  i m p r o v e m e n t was  slightly  larger  PTPA  was  greatly  regular  CNE,  the  (dotted  "peak"  Therefore  the  increased  only  seemed 48.7  for  for  percentage  of  line  No  in  PTPA  'core  2%  achieved with  than  the  3%  F i g . 3.25  the  cannula  potential  (see  the  raised  to  regular  520/400 = in  section  ym  in  1.3  would  the  center  of  The  pickup  radius of  recording.  measurements  an  f o r the  as  below  ym  remark t o the  in  result.  Under  MU SFP  MU, to  PTPA  the  1.3  mm  for  MUP  at y =  are  1%  for  a l l three  the  mm;  of  curve  c o u l d not  be  the core  types.  type  for r  ym, type  the  II  r e g u l a r CNE.  the  I  to  peak  type  shown.  in  an  I as  and  Type  < 2.5  was  mm  I /  extrapo-  ruled  out  radii the  since  would II  MU  fibers  constitute was  0 were r e c o r d e d  of  not  a  a  would  ym  1000  of  location be  at  r  improved  evaluated  because Test  factor (ref.  to at  =  was  measured  ym  910  nicely  ( F i g . 3.24).  cannula'  radius  400  to  I CNE CNE  reduced  improvement  o f 700  type  vs.  pickup  to the  I f the  greatly  'core  The  opposed  assumption  farthest  the  enhanced  3.9).  radius with the  Now  r e g u l a r CNE.  section  type  compared  with  Type  of  the  same  I  /48.7  potential  r e g u l a r CNE  2.5  reported pickup  pickup  to  mm  at  the  errors  resulted  with  than  the =  2.5  II.  type  gradient.  f o r the  improved  up  potential  r  >  cannula  regular, I or  ( F i g . 3.21)  compared  Measurement  520  (see  average  The  made  z  remained  r , compared t o t h e  were a p p l i e d  reality  I,  F i g . 3.22)  about  CNE  3.9) , an  cannula*  were  results  I for large  of  type  for r  type  shown).  of the  either  the  smaller  a very high f i e l d  In  therefore  values  s m a l l e r PTPA t h a n  ( d o t t e d i n F i g . 3.24).  PTPA o f t y p e  Although  was  type  results  r e g u l a r CNE  cannula  3.21)  with  to  the  remote' r e c o r d e d with  'core v s . cannula'  large  vs.  measurements  s m a l l r t h e r e was  with  Fig.  slightly  to record a  ym.  lated  decreased  'core v s .  (no e x p l i c i t  t o t h e more p r o n o u n c e d w a l l e f f e c t .  I/II  of  the  compares t h e  No  a  expected,  as w i t h  3.24  I I CNE.  As  2.5  1300 about mm.  fidelity only  the  measurements  95  I  ' ' ' ' I ' '  0  50  Figure  3.24.  1  ' I  1  1  •  1  I ' ' • • I • i i i ) i i i i I i i i i ! i i i i !  100 150 200 RECORDING D I S T A N C E R  T h e PTPA v s r I a n d t y p e II  (y=o).  250 300 (MICROMETERS)  of the p o i n t e l e c t r o d e , CNE ( ' c o r e v s c a n n u l a ' )  350  regular, ; front  400  type SFP  0 •(  0  i i i i I i—r—i—i—i—i—i—i—i—|—i—i—i—i—|—i  50  Figure  i i—i—|  i  i — i — i — r - i — i — i — i — | — i — i — i — i — |  100 150 200 250 300 RECORDING DISTANCE R (MICROMETERS)  3.25.  350  400  The PTPA v s r o f t h e p o i n t e l e c t r o d e , r e g u l a r , type I and type II CNE ( ' c o r e v s r e m o t e ' , ' c a n n u l a vs remote', ' c o r e vs c a n n u l a ' ) ; MUP.  97  from front and back SFP's at various levels of y (other than y = 0) indicated that  the type  II recorded very  remote' signals as the type  similar  I CNE  (no r e s u l t s shown).  cannula' PTPA of type I and II ( i n F i g . 100  um,  'core vs. remote' and  where the influence on the MUP  3.24)  'cannula  Since the  vs.  'core vs.  d i f f e r e d less than 10% for r <  i s most pronounced, i t was  concluded  that the MU PTPA 'core vs. cannula' of type II must be e s s e n t i a l l y the same as type I. F i n a l l y , F i g . 3.26  shows the deviation i n % from the true MU PTPA (point  electrode) when measured d i f f e r e n t i a l l y 'core vs. cannula* with the regular and the type I/type II (see remark above) CN electrode. The higher f i d e l i t y of the new  designs  I, II i s c l e a r l y  visible,  especially  for r > 300  ym where the  "steepness" of deviation was less pronounced.  Peak-to-peak Duration No  changes were anticipated with the new  design.  Therefore no measure-  ments were made.  Spike Duration Figure 3.27  shows the comparison of the graphs for the SFP  with the point, regular, type I and type II CNE. type I (compared to the regular CNE)  SD recorded  The larger SD recorded with  resulted i n a smaller deviation from the  true value than the regular CNE for r > 200 ym, while for r < 200 ym the type I was worse than the regular CNE.  The type I recorded a longer SD f o r a l l r than  the regular CNE, due to the greatly reduced cannula p o t e n t i a l ( F i g . 3.21) > 100 ys, compared to the regular CNE. AP a f t e r the peak. mining the SD.  for z  The SD i s dependent on the shape of the  Hence the cannula p o t e n t i a l at large values of z i s deter-  140 - i  RECORDING DISTANCE R (MICROMETERS)  Figure  3.26.  T h e PTPA i n % o f t h e t r u e PTPA v s r o f t h e t y p e I a n d t y p e II CNE ( ' c o r e v s c a n n u l a ' )  regular, ; MUP.  U3 00  Figure  3.27,  T h e SD v s r a n d t y p e II  (y=o).  of the p o i n t e l e c t r o d e , r e g u l a r , type I CNE ( ' c o r e v s cannula') ; front SFP  vo  vo  100  The  PTPA,  the  core  however, potential  electrode II  20  with  the  the  r e g u l a r CN value  with  the  II  had  F i g . 3.21.  48.7  differed  of a  ym  20  ym;  CNE a  type  >  250  between  the  r  more  =  300  difference  the  type of  (500  of  only  I r e c o r d e d a 80 a  30  compared  estimated out with factors:  SD type  ys to  ys  longer the  curve II).  ym  I  the  200  of  ys,  extremely  than  T h i s was CNE  type  due  (no  was  short  true  z  SD  MUP  estimate  was  cannula the  SD  ys, however,  type  at  zero  r —  2.5  (about  3%  voltage  z  =  < 150  140  ys  mm  /  at  r  on  the  lowered  ym.  with  brought  up  However, the  differences the  regular  with  at  r  =  type 50  r e g u l a r CN  reduced  type  also  I  by  the  I ym,  only  cannula  contains  measurements were supported  from  dif-  cannula  3.28  than  small  recorded  Figure  was  explained II  a  The  greatly  MU  and  case.  was  type  i t s SD  be  only  potential  value.  complete  The  shorter  can  of  for a l l  deviation  I  » 140  true value while to the  even  type  indeed  for r  f o r the  ym  the  I I around  SD  1%  p o r t i o n s determined  At  true value)  the  of the  AP  core  ( F i g . 3.22).  I I CNE  validity  of  > 350  ym  the  peak  changes).  r  approximately  plotted  the  400  r e g u l a r bare  had  from  SD  where  the  the  the  at the  than  improvement  late  r e g u l a r CNE  are  less  For  to  This  3.27,  potential  ys  type  50  24%  The  regular  The  Fig.  s h o r t e r than  SD.  >  ym  max.  l o n g e r SD  of the  z  Those  Type  -130  < 150  II occurred.  curves  ys  of  only  undergo d r a s t i c  ys.  of  more t h a n  pronounced.  ratio  I and  cannula  SD  potential  same  r =  ±35  15%. in  3.16).  large  ym  than  to  w h i c h was  Fig.  Within  ym  potential  F i g . 3.28  yielded MUP  see So  still at  r  10%  the  for r  values  even below the v a l u e o f  In were  ys  cannula  cannula. SD  of  I but  For  cannula  the h i g h e s t f i d e l i t y .  more  only  ( F i g . 3.21)  48.7  the  never  the  PTPA d i d n o t  with  type  by  almost  electrode.  was  values  ference  SD  s h o r t e r than  potentials for  was  types; t h e r e f o r e the  ys  true  again  to  (which  design recorded the  only  =  i s determined  an  carried  following  SD. (MICROSECONDS) IV) o o  o o  o  \ v\ 4  IS 0  B) H C 3 3T  an > < <B (/I  o •  *><=>  rt- O 0<  ni o a  rt-  a  -* T> < ro ui  (D > — * rt<  •irt>o  •a O r+  IB Z -J m (D -« 13 o - 0— Z0 D mo < + i — to < B UI — ID  3D  cn a CO  m  o < n  (BOO  am  3D  ui rt- 3 3 • C —  o  -  CO  3 0) 1 rt- 0) (D CD -(Q w C  IB T (B 2 c rt- "0 rt(B • < X 73 rt- -) (D • J (B «  — i CO m o • 33 o  o  101  <•  O  cn o o  CO o o  o o  CO o o  03 O o  • 0 < <  o o o  102  -  -  The  MU  CNE  ( F i g . 3.25).  The  far fibers  (this -  -  PTPA  was  z =  140  For  small r,  ys  the  t h e MUP  II  regular where  MU  to  ym  3.27)  case.  SFP's.  of the that MUP  SD  type  by  ment i n t h e  same  the  the was  MUP  the  for r  /  regular  type  the  worst  attributed  type  f o r the  type  I or  description  regular  and  II cannula  type  II  potential  of F i g . 3.25).  much l a r g e r  of  the  around  10  the  the  mm  /  than  type  I  around  SFP  50  ym,  the ym  recording f i d e l i t y .  the  z  to  200  «  type  of the  slightly  100  to  195  II  cannula  and  for r  the  SD  For  50  to  For  very  improvement  I I SD  was  t o 350  true value - a  ym,  rather  the  the  and  15  3.21,  was  36%  mm  /  195  larger  r  and  I I CNE  in Fig.  i n the  SF  value  the  case  in  the  set equal to  the  with type  of the  of  similar. type  i n % from  graph  "peaking"  values  smaller relative  deviation  r =  10  same).  the estimate c o i n c i d e d  The  the  because  potential >  f o r the  estimated type  the  ym  II (in  ys  i n F i g . 3.16  MUP's w o u l d be  electrode.  3.28. from  or  of type  case  r e p r e s e n t a t i o n where t h e same  MUP  corresponding  were a p p r o x i m a t e l y  the  cannula  97.3  the  potential,  II cannula  I I CN  ±20%  also  least  ym  cannula  illustrates  in Fig.  more t h a n  at  48.7  w h i l e f o r r > 300  I and  5 to  estimated curve  case  F i g . 3.29  <  (comparison mm  I and  that  "peaking"  reaches  Therefore at r = CNE  on  SFP  expected  both p o t e n t i a l s  t h e e s t i m a t e as  differed  be  sum  2.5  justify  was  Finally, regular,  =  type  It is a  regular  to  r  than  Those f a c t o r s  I I cannula  is  cannula  z, b o t h  the  same e f f e c t  potential)  cannula  larger  3.28.  type  assumed  for  292  was  i n context with  i t can  core  be  cannula'  ( F i g . 3.21).  i s the  I t can type  (Fig.  mentioned  small r , the  of  vs.  have the  For  %  -  'core  I.  t r u e SD  latter  f o r the  corresponded  e s t i m a t e d SD  never  c o n s i d e r a b l e improve-  140  -i  p o i n t e l e c t r o d e - t r u e SD v regular o type I (• 'core vs cannula' • type I I (ESTIMATE)  130 A 120 A no  A  100 o  CO  100 200 300 RECORDING D I S T A N C E R (MICROMETERS)  Figure  3.29.  The SD In % o f t h e t r u e SD v s r of the regular, type I a n d t y p e II CNE ( ' c o r e v s c a n n u l a ' ) ; MUP. The c u r v e o f t h e t y p e II CNE 1s an estimate, see text .  400  U)  104  Learning  without  Thought  without  thought  i s labour  learning  i s  lost;  perilous. Confucius (Analects)  IV.  CONCLUSIONS AND  RECOMMENDATIONS  105  4.1  Conclusions In  has  t h i s i n v e s t i g a t i o n an  been  ties  of  developed the  about was  found  in  tank model of  an  the  and  recording  Electrolytic  effect";  1964  Pollak,  a,b,c)  tank model i n v e s t i g a t i o n w i t h  literature.  The  m o d e l was  Frequency  axial  dipole  based  on  the  e f f e c t s from the dispersion  was  CN  or  dipole  near  not  specific  unpublished)  1974  fibre  d i s t o r t i n g proper-  tank models f o r  Ekstedt,  impedance";  a c t i v e muscle  re-  but  no  SF  electrodes  report  concept  field  taken  or  in  an  not  be  account  in  could  into  calculations.  Distortions Three  •  ("wall  conductor.  of  electrode.  "electrode  addition,  motor u n i t  Field  580  the  In  needle  experimental  volume  modeled.  measurement  mentioned  example  complete  extensive  the  were  (for a  the  concentric  measurements ported  for  electrolytic  ym  basic  distorting  r e a l dimensions) Shunting  of  pedances. gold  or  lyte.  Therefore  due  shunting  tance  of  weakest Trontelj torting  r of  =  50  a l l  (1979) factor  was ym  compared  a  little  maximum and  mentioned (frequency  were  than  the  elliptic  the  metal-tissue  impedances were v e r y to  the  from 10%  effects.  the  at  bulk  shunting  dependent)  was  the for  but  um  expected.  true r  =  a  PTPA 200  no  a  ym.  for  of  The  for  x  the  electro-  PTPA  decrease  recording  and or  dis-  was  the  Stalberg  and  even  quantitative  im-  platinum,  Shunting  (1964)  possible  interface  large  resistivity  Ekstedt as  (150  investigated:  by  shunting  22%  less  distorting  place  currents  interface  steel only  taking  surface  conductor  specific  stainless  to  leading-off  volume  The  effects  major  dis-  results  were  reported. •  The the  "metallic  wall  leading-off  e f f e c t " or  surface.  The  electrical less  imaging  shunting  of  there  the  dipole  is,  the  source more  at the  106  metallic  surface  increase  due  tic  shape  ("full"  of  56%  PTPA i n c r e a s e  less  see  tioned  the  zero.  Averaging and The  at  a  caused 22%  the  of  a  the  the  full  be AP  SD).  50  after  the  shape  >  ym  size  780  ym.  effect  effect the  of  due  to  results  peak were  much  distortion  was  (1964)  dependent)  <  recording  r  that  Ekstedt  (frequency  r  wall  wall  noted  a  ellip-  finite  for  diminished  Therefore  (shortened  to  PTPA  and  larger  recorded  should  peak.  effect"  For  decreased  It  along  compared  ineffective PTPA  the  metallic leading-off to  the  i s most p r o n o u n c e d in  decrease  recording of  more  simulated  by  Ekstedt  simulated  and  but  also  men-  reported  no  the  far  i n the field  due  to  "pure  distance  of  50  than  720  and  measured  ym.  results  was  near  where  Less  effects  (1973). possible  the  field  with  67% 10%  because  of  a high  field  the  true  recorded were  at  computer  comparison the  the  approaches  from  was  averaging direct  decreases  center  gradient  was  than  of No  at  the  averaging"  ym.  The  Stalberg  potential  surface  dipole  of  the  lengths  different.  individual  "core"  Pt"  was  size  distances  r a p i d l y due  increase  (or a  effect  potential  distances  were The  wall  recording  the  The  results.  measured  gradient  10%  electrolyte.  potential).  Other p o r t i o n s  p o t e n t i a l averaging  surface.  the  the  i n s u l a t o r of  for  paragraph).  around  in  diminished  ym  "metallic wall  quantitative The  the  of  was  50  PTPA o n l y .  by  99%  insulator  r =  than  a pure  over  than  preceding  enhanced  introduced  PTPA  Less  at  insulator of  doubling  "less-than-perfect  were f o r t h e  the  was  increase  insulator.  an  effect  core  PTPA  as  wall  effect;  the  shunting;  •  the  wall  the  The  to the  of  distances  appears  and  compound  f a c t o r s have not  contributions  to  the  AP  been p r e v i o u s l y q u a n t i f i e d .  d i s t o r t i o n s of  those  three  107  The wall  insulation  effect,  "enhanced sized  resulting  wall  was  shunting,  was  i n the order  effect  around  stated that  Overall  complete  up  CNE  a SFP w i t h attenuated  increase  of about  the 'core'  (large  cannula  effect. a  core  over  b y 30% f r o m  10%.  At r =  potential signal).  potential  concerning  that  so  that  r.  This  t h e PTPA i n -  alone  (incorporat-  i n the f a r f i e l d  the increase  resulted  d i d not a l t e r  the cannula  fibers/mm .  evaluation  2  of  was  MU A  um  (after  t h e peak) were  i n a shortened  SD.  much  Ekstedt  t h e shape o f t h e r e c o r d e d  recording  there  cannula  Also  T h e PTPD was  developed  simple  spatial  the contribution t o  was  small  AP.  b y 10% f r o m a  very  touching value was  at r =  even  325  larger See  t h e PTPA,  PTPD  was  an  o f 30% value  directional  ym  than  produced and  just  the core  comment  below  from t h e t r u e  value  a t r = 1600  ym.  representing a small of  im t h e  the true  the cannula)  negative!  a t r = 800  + 25  again  strong  75% o f t h e t r u e  arrangement  r  cannula'  ym t h e r e  t h e PTPD a n d SD d i f f e r e d only  vs.  an a t t e n u a t i o n  only  potential  70% o f t h e t r u e v a l u e was  was  10% o f t h e t r u e  potential.  'core  a n d a t r = 500  (almost  signal  mode  For very  introduced  of the bevel only  value  decreased  The c a n n u l a  i n the f a r f i e l d .  simplified  1800  alone The  was  the true  the d i f f e r e n t i a l  ym, a n d t h e SD o n l y  2-3  "regular"  f u r t h e r deempha-  field,  t h e 'core*  the f o l l o w i n g d i s t o r t i o n s .  A SFP a t t h e back  potential  A  effect  with  AP p o r t i o n s  which  effect)  In t h e near  while  i n the d i f f e r e n t i a l  4 0 % a t r = 1600 ym.  values  t h e peak  the wall  PTPA was  while  Other  additional,  Distortions  The picked  recorded  and a v e r a g i n g ) ,  o f 25% t o 3 5 % .  than  an  f o r a l l recording distances  contribution of shunting.  wall  enhanced  introduced  ( " m e t a l l i c " and " r e g u l a r " w a l l  4 0 % t o 45% o f t h e v a l u e  ing  (1964)  the core  i n a PTPA i n c r e a s e  effect"  the relative  crease  less  surrounding  fiber  the fibers and  SD  density  o f about  facilitated  from  t h e near  the and  108  distant while PTPA 250 a  fibers.  the  PTPD  was um  ys  radii  1979).  longer  able  up  Cannula  the  a  which  SD  to  the  true  at  MU  was  r  =  at  r by  =  um,  and  was  near  SFP,  reached  which  value  is  of  almost  only  Boehle,  to  The  the  true value  field  SD  ' The  at  ym.  r  =  Thus of  the  Stalberg  and  the  r =  - a  90%  half  1975;  already at  far  •*• 25  about  attributed  but  and  for a l l r.  for r  investigation. ym  55%  a  of i t s value  (Thiele  50  the  from  50  determined  model under  shorter  as  o n l y 5%  literature  value  was the  greatly  and  tial  were  This  means t h a t  when  potentials distance  10%  of the  core produced core  a  fibre case  the to  65%  of  f o r the  later  fiber  potential  on  relatively  was  250  about  40  the  CNE  ym  rather  was of  close  a MU,  of  to  where  consider-  the  core  was  between  different  generator at a f i x e d  relation-  over  approximately  propor-  the  cannula  of  were 50  but  the  large  are  but  the  MUP  core.  the  core  many f i b e r s  near  values.  Cannula  where  the  ym  ym.  SF  (after  the  poten-  the  near  measured, t o 400  to  core  f a r from  r only a cannula p o t e n t i a l  p o r t i o n s of  fibers  of the  fibers  t h e MUP)  reach  absolute  of  100%  cannula  o n l y a few  r =  was  position  the  can  PTPA  for  well  part  potential  changes  However,  relative  potentials  small  decrease  depth.  the  same v a l u e s o f  For  undergo  o n l y one  insertion  cannula  nearest f i b e r  PTPA.  to  t o t h e most s i g n i f i c a n t  cannula, of  in  The  Cannula  i n the  contribute  large  found  dependent  cannula.  found  was  surface.  increase  core  the  was  when c o n s i d e r i n g  pickup  to. t h e  potential  of  PTPA was  ym  potential  depths  the  tional  the  value  same  in  distortion.  cannula  insertion  (which  the  distorted  the  smaller observed  of  than  were  Potential  The  ship  true  400  The  density  shape  um  of  SD  essentially  the  400  and  reported i n the  fiber  picked  of  radius"  Trontelj, small  75%  at r =  "pickup  PTPA  remained  about  and  pickup  Both  A of  the peak),  recording facing  0.5% the  to  the 4.5%  cannula  109  potential r) while effects  was  up  i n the  to  practically  100%  case  of a f a c i n g  SF  of those  described  above.  insertion  depth,  and  the  vs.  cannula'  large A  the f a c t  has  that  proximity  been  of  assessment  in  PTPA  depth  nearby  of  potential  at  were t o d i s t o r t  and  the  fibers  of  cannula SD  p r e v i o u s l y done.  insertion  number  core  z =  c o r r e s p o n d i n g v a l u e was  arrangement,  distortion  the  and  fiber  not  the  the  cannula p o t e n t i a l s  quantitative  MU  resulting  MU  of  of  the  about  the  relations  potential the  Special  cannula  to  the  less  cannula.  60%.  between and  differential  i s of  us ( a l l  SD  amplitude  signal  'core  laid  importance was  as  cannula  s h o u l d be  This  The  PTPA a n d  shape  emphasis  750  on  than  the  hitherto  un-  documented.  Electrode  Improvements  Finally, ledge  into  hibited An  a  with  new  greater  distal  the  regular  CNE,  for  and  than  radius"  various  neuromuscular  10%  by  small  radius  of  the  possibly  up  the  true value  to at  the  CNE  25%. 250  um,  a  higher  came  off a closer  regular  CNE  which  This not the  is  a  obvious  of  the  opposed  improved 45%  of part  great  deal of  the  the  true  important  represents  a  CNE with  the  CNE.  than  the  only  The  reached  the MU the  because MU.  about  portion almost  The 5%  extended  larger  the  The  extending  of  is  "harmful"  feature  section  1980).  ex-  that  value  in  know-  also  unchanged.  resulted  i n any  Antoni,  t o the  realizable  remained  very  above  annular  therefore represent SD  the  the  to  r e g u l a r CNE and  took  easily  for  PTPD  (Stalberg  as  except  which  recording f i d e l i t y  The  of  MU  more  MUP.  would  The  seemed  shielded SD  um.  radius  territory  r =  and or  520  were t e s t e d  cannula,  disorders are  improved  MU,  SFP  to  pickup  o f t h e w h o l e MU  the  with  30%  towards  PTPA  a  CNE  that  insulation,  Both  "pickup  relatively  of  either  larger  the  design  end  core  potentials.  was  The  of  improvement  cannula  PTPA  designs  account.  insulated  flush  two  to  pickup of 90%  r e g u l a r CNE.  the of For  110  smaller the  r,  a  regular  worst  CNE  case  estimate  w h i c h was  about  of  10%  the  SD  approached  l a r g e r than  the  the  true  value  value  recorded  (r =  50  with  um) .  Summary Thus the •  The  m a j o r new  q u a n t i f i c a t i o n of  effect"  (for acrylic  "shunting"  was  leading-off •  •  The  findings the  weakest  of  the  cannula  SD).  The  p o t e n t i a l was  •  motor  unit  considerably  the  The  far  smaller  A  insertion  simple  way  electrode  Pt)  of and  field  volume  conductor  currents",  "potential averaging"  distorting  effect  at  "wall  showed the  that  metallic  disturbed  the  picked  by  up  amplitudes  i n the  far  the  field  appreciably  concentric  near  field  and  (smaller  needle  electrode  spike  durations  field. depth  of  cannula p o t e n t i a l than of  was  was  in  the  far field  the  the  improving  designed  SD  the  of  the  (SFP  proximity the  and  near  and  cannula  was  and  recording  of  number o f fidelity  experimentally and  far  field  much  less  influence  nearby  fibers.  of  the  tested.  (SFP  and  The MUP)  on  concentric main  and  in  the  needle  improvement the  PTPA  of  MUP).  Recommendations The  promising  type  II  new  gated.  Especially different  annular  cannula  because  i n p r a c t i c e the  3.20  and  PTPA, PTPD a n d  in  4.2  "shunting  glass  the  i n v e s t i g a t i o n were:  surface.  presence  with  •  in this  shows.  The  portion  at  regrinding  design  could  i n s u l a t i o n lengths  the  bare  CNE  tip  should  cannula of  the  be  portion  t i p and  be  and  more  modifications  tested. might  removal  thoroughly  The  not  be  of  the  latter as  in is  investithe  important  c l e a r - c u t as  burr  as  bare  well  as  Fig. the  111  use  of  shaft  the  needle  around  the  Comparisons one  would  Other  a  large  hopefully  number  cause  of  confirm the  be  sought  to  an  testing  of  results  from  results  develop  i s an  abrasion the  the  insulation  regular  CNE  and  the  electrolytic  the  A  the  urged. improved  tank  "optimal" electrode.  t o reduce  at  design i s strongly  i n the  another  example  new  a  found  of  model.  "double-  directional property  of  CNE. investigations  described  in  Table  diameters  of  0.3  (examples  from  to  leading-off  extremely  were  2.1.  mm  It  surfaces Also  small  the  made  with  other  Commercially  0.9  DISA).  investigation. an  to  Clinical  t i p , i f realizable,  No  and  likely  bevel.  ways m i g h t  bevel" the  of  are  and  can cause  Pt  be  available  expected  of  the  of  than  0.015  to  smaller cannula  properties  only  CNE's  e l e c t r o d e s come  distortions  the  of  of  areas  that  different  area  CN  leading-off  measurement  leading-off  types  0.0005  to  in  one outer  0.07  mm  diameters  than  measured  of  SF  a  the  in  this  electrode with  0.0007 mm  would  be  of  order  to  interest. A  few  improve  recommendations  the  measurement  concern  accuracy,  the the  experimental following  apparatus.  points  should  In be  taken  into  consideration: •  Variable voltage in  •  amplitude should  not  of  the  exceed  dipole certain  current limits  I. (see  For  small  f o r example  o r d e r t o s t a y out of n o n - l i n e a r e l e c t r o d e impedance  The  dipole  minimum  current  shunting  amplitudes, •  Variable  and  •  Effective  a  Temperature  frequency  without  used  running  should the  risk  be  carefully of  noise  amplifier  gain.  filtering.  control  of the  electrolyte.  the  measured  Plonsey,  1969)  effects.  too  causing non-linear electrochemical processes. calibrated  r,  evaluated  slowly  for  changing  112  In tank of  another  with  a moving  frequency,  still  not  (which  be  the  account  the frequency  dipole.  the  the  latter,  of  the  bulk  ratio  impedance)  but  handling also  much  more  a r e f o r example  averaging  as  given  distortions,  a as  function a  be  features  the three of  function  not just  of  the of  PTPA d e c r e a s e s  measured  the  electrolytic as  a function  of shunting  would  concentrations  electrolyte  and  the  interest. with  only  the  recorded  order  z  computer  could  effects  length/time  r ) , in  i n an  electrolyte of  Not  basic  be  similarity  different  techniques  easier.  modeled  could  resistivity  w o u l d be o f  s o p h i s t i c a t e d measurement data  could  the shunting  For  Important  were  Then  effect  the problem of the geometrical  solved.  interface  More make  where  affect  specific  step,  or increases.  d i s p e r s i o n be  AP's  could  of shunting,  (most to  acquisition  results  thoroughly  be  would  taken  into  extracted.  wall effect  of  those  assess  the  and  effects shape  113  BIBLIOGRAPHY Adrian J  ED & B r o n k DW ( 1 9 2 9 ) . 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Potentials  117  Waring  W  (1974).  cal  Observing Signals  E l e c t r o n i c s Technique;  Academic P r e s s , Weber E  (1950).  I n c , New  J  &  Mahler  Electrodes. Med E l e c t r o n Wiechers  DO,  J  Biol  Blood  JR  (1964).  &  P h y s Med  Rehabil  (p 215  in:  Biomedi-  et a l ) .  Theory  and  Applications.  York. An  Analysis  of  Electrical  Properties  of  Metal  2:299. Stow  RW  Impedance. Arch  Muscle  York.  I n c , New  Eng  and  & P r a c t i c e , ed H M i l l e r  Electromagnetic Fields.  John W i l e y & Sons, Weinmann  From Nerve  Theory  60:364.  (1979).  EMG  Needle  Electrodes:  Electrical  118  APPENDIX  119  + 15V stab. Q  ^3 5 6  7*/C  5 2 N 4-920  OP, 2N4-126  sky  Exact IZ5A  0  X/' OP,' 2N4-124-  so:  8.2  2N4-925  fkt,  56  - / 5 V-Jt*lr.  FIqure  A . 1 . The c i r c u i t  of  the current  source  (section  2.6).  120  Figure  A.2.  The c i r c u i t  of  the  amplifier  (section  2.6).  1 : 1  115 V ~ 60 Hz  F 1 gure  A.3.  The s i g n a l f l o w c i r c u i t of the complete electrical a p p a r a t u s . Shown a r e t h e u n d e s l r e d c u r r e n t s In c a s e of no I s o l a t e d power s u p p l y f o r t h e d i p o l e c u r r e n t s o u r c e . A l s o shown i s t h e common mode voltage Vcm at the ' c o r e ' and ' c a n n u l a ' of the CNE.  


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